System for Location in Environment and Identification Tag

ABSTRACT

A system for location of animals and/or objects in an environment includes a signal processing and signal generation system consisting of electromagnetic tags on animals (or other objects) in an environment (typically a three dimension outdoor natural environment) where the animals or objects are physically present at arbitrary locations, and an electro-magnetic signal generating, signal receiving, and signal processing system that can move through or in relation to the environment. The system can compute the location and identity of the animals or objects based on signals received from their associated tags, including the calculated location of the ID tags, which function as “Reader-Locators.” The calculated location is enhanced by information about the environment provided by maps, satellite photos, GPS, GIS and/or other data specific to the probability of the location of the animals or objects within certain regions of the environment. The system includes a physical and electromagnetic modeling operation that is interactive with the environmental information derived from the actual environment, either historically or in “real-time” as the monitoring process occurs.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/345,282 filed Nov. 7, 2016, which is a continuation of U.S. patentapplication Ser. No. 12/287,218, filed Oct. 6, 2008, now U.S. Pat. No.9,489,813, which is a continuation-in-part of U.S. patent applicationSer. No. 12/148,215 filed Apr. 15, 2008; which is a continuation-in-partof U.S. patent application Ser. No. 11/904,035, filed Sep. 24, 2007which claimed the benefit of U.S. Provisional Patent Application Ser.No. 60/846,687 filed Sep. 22, 2006, and U.S. Provisional PatentApplication Ser. No. 60/994,937, filed Sep. 21, 2007, all of which areincorporated by reference herein, including all appendices thereto.

STATEMENT OF GOVERNMENT INTEREST

The development of this invention was supported at least in part by theSmall Business Innovation Research Contract No. FA930206M0012.Accordingly, the United States Government may have certain rights in thepresent invention.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an electronic identification andtracking of mobile or arbitrarily located objects, particularly wildanimals, within a three-dimensional environment. Its primaryapplications involve automated tracking from distances of “zero” up to 1km or more using small, light-weight devices (tags) that require nodirect power source or regular maintenance or servicing.

Background

This disclosure describes an improved system for tracking and uniquelyidentifying individual wild animals and other objects. Tracking wildlifehas become an extremely important tool for studying and managing bothendangered species and animals of economic and scientific importanceincluding wildlife and pests. Traditional methods of tracking wildlife,using VHF transmitters, are problematic because they often requirepost-processing and triangulation to calculate location with widemargins of error, involving much wandering or meandering to locate asignal, and use transmitters that are often too large or heavy to beused with much efficiency on small or growing animals.

SUMMARY OF THE INVENTION

A goal of the present invention is to achieve a system that will provideidentification and location information for objects or animals, such asdesert tortoises, within a defined geographic area and over a definitetime-period. A thorough consideration of the available and emergingtechnologies lead the present inventor to conclude that a combination oftechnologies is preferred as most appropriate to satisfy a three-stageor multi-stage process for tracking (or locating) objects such astortoises.

Stage One involves acquiring location, and perhaps identity, data likelyfrom an airborne platform (e.g., airplane, UAV, satellite, etc.) thatwill cover the entire study area relatively quickly and greatly reducingsignal loss and degradation from ground and vegetation effects. Thiscould possibly be done by using temporary mast-mounted antennas in fixedlocations, to be moved sequentially through the study area during thesurvey process, or moving arrays of antennas with fixed or known spatialrelationship to each other. GPS data maybe gathered regarding thelocation of the arrays, or individual antennas.

Using GPS-based data from Stage One, Stage Two would use a small ormid-sized vehicle, such as an SUV, van or all-terrain vehicle. StageThree would use a lightweight backpack-mounted receiving system, withshort-range antenna, borne by a person, robot or moving platform such asa Segway® transporter, to hone in more on the study objects or animalsfor more accurately to provide real-time location and possiblyidentification. If an aircraft is not available or allowed, a two stagesystem may be used (ground based mobile vehicle and backpack mountedapparatus).

Finally, Stage Three would allow for direct observation and retrieval ofthe study animals and guarantee positive identification. The tortoiselocation and ID project which provided background application for theinvention precluded the use of fixed structures like towers, since theseprovide nesting and observation platforms for their worst predators;ravens. For this reason the “mobile” approach was mandated.

The present inventor considered use of a simple combination of two oreven three different technologies such as a harmonic radar tag andpassive RFID to provide locating functionality at medium to long range,and individual identification at close range. The present inventordetermined the practicality of combining functionality into a singlepackage or a single device, such as a passive or active RFID tag thatalso functions as a harmonic radar target, and other combinations ofrelevant technologies and associated apparatus.

As noted above, an objective of the preferred embodiment is to achievethis extremely high performance through a systems approach, in whicheach component of the system is an integral part of the process and theefficiency and accuracy of the readings and the design process isconducted accordingly. Such a system consists of several components orsubsystems: 1.) tag(s) (transmitting device(s) located on a tortoise orother wildlife or object); 2.) reader (receiver to “activate” tag andreceive data or to simply receive data); 3.) data interface; 4.)computer system; 5.) “dynamic database” consisting of data storage,complex computation, presentation, and real-time interpretationcapabilities; and 6.) real-time bi-directional data transmission networkbetween all “reader” devices or stations and the main database, andutilizing non-interfering data gathering signal frequencies or protocolsbetween tag and readers. The design features of each component of an“ideal” system are constrained by a series of (1) tortoise; (2) (objector asset), reader (or data-gathering station); and (3) study-imposedconstraints, as discussed above. Depending on the embodiment, frequency,bandwidth, and other signal generating, coding, and propagation factorsare made to yield the optimum combination of transmission range locationaccuracy, power-efficiency, etc. within constraints for lawful andpractical operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative flow chart of how the entire described systemfunctions to detect, identify, and locate the tracking tags inthree-dimensional space, and represent the data in a dynamic database.

FIG. 2 is a diagram showing the design of the field lab and trackingvehicle with antennas attached for transmitting the interrogation signaland receiving the signal from the tags, as well as communicating withsecond or third-stage data gathering stations.

FIGS. 3A-3G are drawings of transmitting tags and receiving systems.

FIG. 4 lists some important design features incorporated into thedescribed system.

FIG. 5 describes a process by which information on the tag's identity,direction, distance and location are received and processed by thedescribed ID and locator system.

FIG. 6 is a flow chart representing an embodiment of how the receiversignal processing and probabilistic spatial filter work to improvedefining the location of the tag.

FIG. 7 shows a parabolic antenna, although other reader antennas may beused such as Omnidirectional, Directional, Polarized, etc.

FIG. 8 represents the signal structure of a pulsed modulated signalmeans for encoding the tag's identity.

FIG. 9 represents the physical structure of a frequency-modulatedcontinuous signal means for encoding the tag's identity.

FIG. 10 is an example of spatial location map with the tag and readerlocations and a distance/direction line drawn between them.

FIG. 11 a computerized model of a tortoise shell with a “patch”tag/antenna designed to fit on a single scute of a juvenile deserttortoise.

FIG. 12 is an oscilloscope tracing showing the time-of-arrival detectionin the locator system antennas from a single signal sent out by a singletag.

FIG. 13 is a sample tag commercially available with numerous componentsincluding a light sensor, signal processing circuit, and visible LEDs(Light Emitting Diode) in such size that could fit on a juveniletortoise scute.

FIG. 14A is a photograph of a telemetry tag mounted on a scute-shapedconductive patch antenna (left) and a VHF transmitter (middle), and alow-frequency passive integrated transponder (PIT) tag (right) shown forsize and shape comparison.

FIG. 14B is a photograph of a VHF “beacon” transmitter mounted on adragonfly, functioning as a telemetry tag to track dragonflies inflight.

FIG. 15 is a photograph of a mock-up patch-like tag on a juvenile deserttortoise shell.

FIGS. 16A to 16D provide a diagram of function of a combined harmonicradar and RFID tag and idealized traces of emitted signals in the On andOff states. Specifically, FIGS. 16A and 16B show a combination ofseveral RF modules to create a multifunctional tag with RFID andHarmonic Radar capabilities, and FIGS. 16C and 16D show a carrier signalis seen in the data stream as a series of on and off periods dependanton the presence of harmonics.

FIG. 17A is a diagram of a “series” version Harmonic Radar, RFID tag.

FIG. 17B shows an internal system structure for an RFID tag whichemploys a “switch” to modulate the harmonic radar diode output by“ON-OFF” keying.

FIGS. 17C-17G depict various switching configurations that may also beused to enhance transmission and stability properties of the tag.

FIGS. 18A to 18E are diagrams of “RING” tags in alternative versions oftype and complexity from “resonant rings” to semi-active harmonic RFIDradar tags.

FIG. 19 is a diagram of an energy harvesting Harmonic Radar/Semi passiveRFID tag with wake up signal circuitry.

FIG. 20A is a diagram of harmonic RFID radar tags with inductivecoupling.

FIG. 20B shows an internal system embodiment of an example tag circuit;

FIG. 20C shows a diagram of tag signal output vs. activating fieldinput.

FIG. 21A is a diagram of a “scheduled” transmitter tag.

FIGS. 21B and 21C are diagrams of energy harvesting passive “flashbulb”tags.

FIG. 22 is a diagram of two patch transmitter tags on a tortoise shellshowing a synchronized resonant antenna system with transmitters ondifferent scutes.

FIG. 23A is a diagram of a “patch antenna” transmitter tag in oneembodiment.

FIG. 23B is a diagram of a “patch antenna” transmitter tag, in oneembodiment, showing how it would be attached to the shell of a tortoise.

FIG. 23C is a diagram of a “patch” tag showing an example schematicdiagram.

FIG. 23D is a diagram of a “patch” tag in a “triple technology”embodiment.

FIGS. 24A to 24B are diagrams of the solar power components mounted on apatch transmitter tag, including the tortoise as a “bio-electrical”component.

FIGS. 25A-25B are diagrams of another embodiment of the solar powercomponents of the patch transmitter tag, in which light is focused ontoa photo-sensitive portion of an IC tag, including photo-active materialin the focusing apparatus.

FIG. 26 a is a diagram of a multi-spiral antenna attached to a tortoiseshell.

FIG. 26 b is a diagram of patch transmitter tag with a pointed emitter.

FIG. 26 c is a diagram of patch transmitter tag with a pyramid-shapedemitter.

FIG. 26 d is a diagram of patch transmitter tag with a dome-shapedemitter.

FIG. 26 e is a diagram of patch transmitter tag with a combinationpyramid/domed-shaped emitter.

FIGS. 27A to 27F, except for 27D, are diagrams of various antennasarrangements arranged or attached to a patch transmitter tag.

FIG. 27F is a ring-shaped harmonic-generating antenna.

FIG. 27D is a diagram of a synchronized set of patch tags arranged tomaximize signal transmission efficiency.

FIG. 28A is a diagram of an elevated wire antenna element on a patchtransmitter tag.

FIG. 28B is a diagram of a patch transmitter tag with a hinged antenna.

FIG. 28C is a diagram of a solar-activated bi-metallic coil for thehinged antennas depicted in FIG. 28B.

FIG. 28D illustrates how a tortoise's domed body can be used asdielectric material between two synchronized tags.

FIGS. 29A, 29B are diagrams of a patch transmitter tag with pyramidalemitting electrodes.

FIG. 30 is a diagram of a synchronized set of patch tags arranged on atortoise to maximize signal transmission efficiency.

FIG. 31 is a diagram of a synchronized pair of patch tags arranged inspace to illustrate maximization of signal transmission efficiency.

FIG. 32 is a diagram of a synchronized pair of patch tags arranged ontortoise shell to maximize signal transmission efficiency.

FIGS. 33A to 33C show an embodiment of a solar activated transmittertags.

FIGS. 34A to 34H show an embodiment of various tag and antenna shapesthat can fit on a “scute” of a desert tortoise.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

In light of the difficulties with using any one particular technology tosatisfy all of the needs of this system, a multi-staged process ispreferred. For example, a wide beamed interrogation signal would beemitted into the area to stimulate a passive or semi-active tag totransmit its signal with sufficient energy to be detected up to 1 kmaway. In addition and alternatively, a self programmed beacon signalwould be emitted by the system that would then be switched to Stage-two,which would more narrowly beam a more directed signal to the desiredtag, thus stimulating location and identity information from a separate,RFID-based passive tag, which can be received at 30-100 m or more. Forwildlife applications, we also recommend for life-long identityassurance, a traditional low frequency ultra miniature (8 mm×2 mm)(e.g., 134.2 MHz) RFID tag be implanted into all animals foridentification at distances of several cm up to approximately 1 m.

Tracking Tags The tracking tag is a unique design that combines one ormore battery powered beacon signal generators in addition to otherID/location signal generators. The signal generator would be operated bya combination of scheduled transmissions initiated by either an internalclock-calendar integrated circuit (IC) and/or an externally generatedwakeup signal generated by readers. The system would include semi-activeUHF or VHF tag generating either in backscatter, harmonic reflective, oractive transmission made in response to an RF interrogation signalemitted by a reader unit at mid-range, likely 1 to 50 m. Power forvarious tag operations is obtained from a primary battery, secondarybattery, or super capacitor energized by energy-harvesting elements onthe tag (such as photovoltaic cell, motion sensing microelectronicgenerator, or RF absorbing and rectifying apparatus), for obtainingpower from an ambient RF signal from a nearby interrogation unit. Themedium-range function may also be a SAW element, which is mostefficient, and not an “active” electronic circuit; (HR) harmonic radarreflector element; standard UHF-RFID IC; combination SAW-HR-RFIDelement; or, in certain situations, the beacon transmitter could beactivated by sufficiently powerful external energy supply (sunlight ornearby RF source and wake-up signal).

In the preferred mode of operation, the tag will spend most of its time(as does the tortoise to which it is attached) in a sleep mode. To savepower and increase the life of the unit, a clock-calendar (which runsfor the operational life of the tag, supplied by the primary batteryplus any other energy that can be harvested and diverted to it) has asleep-wake schedule programmed into it at the time of deployment. Duringperiods of time pre-arranged for the location/ID surveys by the surveyscheduling teams (or computer algorithm), the tag status shifts to areceptive condition. This means that the tag can be activated totransmit a beacon signal, presumably at a time when population surveysare planned to be conducted by the project team.

If the tag is exposed to sunlight, or energy is generated by tortoisemovement, then the internal solar cells will charge either a secondarybattery or a super capacitor to provide enough energy for a strongbeacon signal. The presence of sunlight also means that the tortoise isabove ground and signal transmission is likely to be at an optimumcondition for reception by a distant receiver-reader. If there is nosunlight (or energy harvest of other type) during the receptive timeperiod, then the tag can emit a lower-level beacon signal at a specifictime period, which will provide a worst-case opportunity for surveyorsto detect a signal and take other measures to locate the tag (likely byperforming a more detailed sweep over the general area in which thesignal is detected). The beacon pulse from the tag may be a short burstof RF signal from an RF oscillator tuned to a specific frequency, or itmay simply be an impulse into a highly resonant antenna that willgenerate an exponentially decaying burst at the selected frequency.

Beacon pulses can be combined in timed pairs to provide ID informationin addition to a location burst. The first pulse of each sequence isprovided according to a relatively long (e.g., 1 to 10 seconds) timeinterval. The second pulse is provided at an “identifying” time intervalwith respect to the first pulse.

A sequence of these pulse-pairs is repeated over a period of time (forexample 1-5 minutes) in which many repetitions of the pulse codes aremade. The tag is decoded by the reader based on the proportionality ofthe time between the two pulses. Since many tags may be present andactive at a given time period, the pulse codes are to be designed sothat tag ID indeterminacy is eliminated. Given the relatively smallnumber of ID codes, the short time-length of the signal pulses and therelatively long time gap between pulses, such a “collision-proof” codesystem will be feasible.

An active tag includes a battery and sends a burst signal on receipt ofa stimulating signal or at a pre-programmed time interval. It would bepossible to recharge the battery at close range with the tortoise heldin the charging field using energy harvesting. Tags functioning in the900 MHz and 2.4 GHz bandwidths may be able to take advantage of existingactive and passive radar technologies, including ground-penetratingradar, however, a strong burst signal could be possibly too strong to besafe for the tortoise, but not for other non-endangered animal orinanimate objects. Energy harvesting sources for recharging active tagscould include the sun or a microelectronic mechanical system thatrecovers energy from the tortoises' movements (much like a self-windingwristwatch, except generating electrical charge for storage or immediateoperation).

The tag also includes a passive or semi-passive element for location atintermediate range (1-30 meters) to save energy from the battery whenmore frequent integrations and responses are needed to located the tagprecisely from an intermediate range. This may be a SAW (surfaceacoustic wave), harmonic radar, energy-accumulating discharge“flashbulb”, standard passive UHF RFID, or combination. This allows thetag position to be located exactly once the long-distance locatingsystem has determined its most probable area of location and a person(or robot, etc) with a “hand-carried” medium/short range locator/IDreader has moved close to the location that was predicted. No energyfrom the tag's primary battery is required for thismedium-to-close-range location technique. One possible embodiment isinductive coupling of the code generator to the antenna using a coupledinductor to another inductor that also functions to tune the resonanceof the harmonic reflector circuit, and frequency conversion may be asneeded, such as 114 or 164 MHz.

A recent technological advance is the ultra miniaturization of 164 MHzradio transmitters used since the 1960s for tracking larger wildlifeincluding adult desert tortoises. One recent study effectively affixed0.600 mg battery-powered radio transmitters to dragonflies (and studieshave been done with sparrows). Although the operational life of the tagswere only 2-3 weeks, their effective tracking by land vehicle andairplane suggests that this traditional radio transmitter technology canpossibly be used after further modifications, according to the presentinvention.

Energy harvesting, micropower clocks, improved antenna design, plus anumber of recently evolved enhancements to the reader/locator systemincluding a spatial probabilistic data filter and processing system, canall potentially result in successful use of this technology according tothe length of lifetime and effective range requirements. One significantadvantage would be that biologists might be able to use existingtelemetry equipment, thus saving financial resources in projects thatmight not require the high accuracy and long life of the presentrequirement, or could be used in conjunction with or in addition to thereading/locating equipment of the present invention in cases in whichthe location of the animal or object has been determined recently, andnot much variation in location is expected.

The tag for tracking tortoises would be designed to fit on a singlescute of a juvenile desert tortoise. The tag base can function as apatch antenna. In addition, one or two wire antennas could additionallybe attached to the tortoise shell on a number of scutes, but permittinggrowth of the tortoise by a flexible wire that can be pulled throughseparate guide-tubes on each scute as the tortoise grows. Tags can becustom designed to any particularly animal species or other asset thatneeds to be tracked, in terms of size, distance of location, taglongevity, power supply, mounting on animal or object, etc., within thescope and limitations of the invention described within.

A signal received by the tag from an activating reader antenna, whichcan be at a resonant frequency of the tag's antenna (likely 165 MHz, 916MHz, 2.4 GHz, or microwave), including other bands in which licensedoperation is not required, would activate a passive diode-detector“switch-on circuit” or “wake-up” (which requires no operating power fromthe battery-powered circuit).

The tag thus activated would emit an additional, closely spaced seriesof RF bursts. The reader will be within a relatively close range (1-100meters). When the tag is located, found and accessed it can bere-programmed and possibly re-charged using a reasonably strong RF fieldor light source over a period of several minutes. Even if no solar poweris available, the tag can be instructed to use power from its primarybattery to perform re-programming of tag data to alter the initiallypre-determined “beacon” signal schedule.

The schedule override may be activated optimally from an aircraft basedplatform, sending a strong microwave signal towards the ground andmoving across a “grid” pattern to cover all area to be studied oractivated for un-scheduled surveys. This method can also be utilized forthe scheduled surveys when the tag is in the receptive mode already, tomore precisely trigger the timing of tag transmission of beacon burstsand thus economize more energy. In the absence of an aircraft-basedwake-up operation, the operation might have to be performed by vehicleor hand-carried apparatus at much closer range than permitted by thespecified 2 km road spacing indicated in the tortoise tracking system ofthe invention. Other systems might have different specifications.

Receiving Reader-Locator and Antenna System

Tag readers-locators and the structure of the data encoding the IDinvention are integral parts of the same system. The reader must be ableto send an optimal interrogation signal of the appropriate frequency andamplitude to stimulate the tag device (except for scheduled tag-beaconsignals). In passive RFID and Harmonic Radar systems, the interrogationsignal must also include sufficient power to energize the tag to operateeffectively and send its encoded or beacon identification. The readermust then be able to detect the returned signal or beacon and decode andanalyze it to determine the tag's identity (for RFID) and/or itslocation.

The reader consists of: 1) electronics package for energy transmissionand and/or data to the tag, 2.) Antenna or antennas: at least one forsending power and/or interrogation signals, and at least one (or more)for receiving tag signals. The same antenna might in some cases be usedfor both sending and receiving. 3.) Receiver and analog signalprocessing for acquiring tag signal and a digital processor for digitalsignal computations, and 4.) two-way independent of tag communication,RF communication of reader data to main system or other communicationnetwork nodes.

One subsystem of the tortoise reader system is a receiver-only system,if the tag (or one of multiple tag devices) is self-activated orotherwise independent of a reader signal (cf., active RFID technology ortelemetry beacon signaling). The reader antenna system, consisting oftwo or more antennas mounted on poles at a distance of at least 3 metersbetween antennas, will likely be vehicle-mounted for widest range. Thisportable version would probably use a single directional antenna. Theantenna would likely emit a RADAR interrogation signal and possibly anRFID type signal, if needed for close-up identification. In addition,the hand carried unit may contain one or more temporary antenna stationsaffixed to short poles or a tripod and would be in communication withthe on-foot researcher and the mobile laboratory. These combined antennalocations can provide for triangulation of the signal source to furtherimprove range and accuracy.

For example, the on-foot researcher would have a mobile locating deviceand optionally an auxiliary fixed point antenna. The antenna might beplaced in a fixed position where a possible clear signal is firstreceived. It would either have its own GPS/compass or itslocation/orientation would be entered by the on-foot researcher. Theon-foot researcher then proceeds in search. The signals received by thefixed antenna would be transmitted to the locator computer either in themain lab vehicle or locally to the researcher location device. Thisenables powerful triangulation and time-of-arrival data from two/or morelocal receivers as opposed to just one. Alternatively, a single antennacarried by the researcher may be used as the search device.

The on-foot researcher also employs appropriate transport vehicles foruse in difficult terrain, for example the Dean Kamen patented, U.S. Pat.No. 7,131,706 and other two-wheeled self balancing transport device.Also numerous new miniature aerial remote-controlled vehicles could bedeployed to operate at low altitude by researchers.

It should be noted that a probabilistic spatial filter may be used inwidely varying location acquisition contexts. For example, if the surveyperiod is relatively frequent compared to the speed of the tortoise (orobject or asset being tracked) then a factor of the location probabilitywould be the maximum distance that the tortoise (asset or object) couldhave traveled in any given direction, from the time of its lastconfirmed location, based on its “top speed” and the time elapsedbetween surveys. This calculation can be further refined by referencingthe terrain map and compensating for topographical factors that precludetravel in a given direction to set a limit on a “top speed” of movementin that direction.

In cases where the asset is fast-moving (hundreds or thousands mile perhour) and surveys are the high frequency (second, milliseconds,microseconds, etc) this same technique still provides computationaladvantage over other location-projection mechanism.

In addition to location, the same method might just as well provideprobability of direction and speed traveled, or other information aboutaspects of location and trajectory that can be related to “known maps”and characteristics of the animal, asset or object. Finally, it shouldbe noted that even without a location or a data tag on the animal, assetor object, the PSF (Probabilistic Spatial Filter) method is stillapplicable, as long as its (animal or asset) possible location can beestimated by any signal acquisition method (radar, etc) and any dataregarding the probability function of an object in the 3D space exists,and any prior location information (exact or approximate) regarding theobject exist. This extends the utility of the PSF to virtually anylocation system that can derive a signal from the animal or assets withor without a prior knowledge of identity.

Operationally, the system would work as follows. One or more trackerswould be looking for the beacon signal from the air or a ground-basedlab-vehicle, using a sensor network and real-time computer-based map.When a signal is received, the tracker's location and/or telemetry isrelayed to the database along with the exact time of detection andinformation (if any) of the direction and distance to the tag. The dualantennas on the lab-van would allow for signal detection and directionfinding by at least one or more of: time-of-arrival, phase, and signalstrength or other detection signals. The database stores the informationand compares it to a map or other coordinate location reference. Thedatabase computes the direction and distance to the object based onhistorical data, reported observations, and computer model of tortoisehabitat. The database then sends probable location data to the trackerswho use it to refine their search. The process continues until theactual location is determined.

Signal Processing Database and Probabilistic Spatial Filter (PSF)

The dynamic database, programmed within the receiver system, would servetwo sets of functions using essentially the same dataset. It can bepre-loaded with all available GIS-based and other spatial data about theterrain, from various resources and also updated with real-timeinformation during the search (photographs, video, etc.). The firstfunction is a probabilistic spatial filter to be used in conjunctionwith real-time data from the antenna system in connection withpreliminary location calculations. These data would pre-define theprobability function of a valid signal from a tortoise within theterrain. The probability function would be based on a prior knowledge ofthe terrain features, previous data, if any, on tortoise or burrowlocations, and a probability function of tortoise location based onterrain features and tortoise knowledge. For example, a probability of0.0 would be assigned for inside a large boulder; 1.0 for flat ground inthe open near a burrow, 1.0 for foliage patches known to be attractiveto the tortoises. Probability values between 0 and 1 may be used basedon finer gradations of knowledge of the geographical and other featuresin the area, and the baits of the animals or usual movement trajectoriesof objects in and through the area or volume. For example, variablelikelihood will depend on known tortoise presence at each location basedon historical data from the local tortoise population. When a beaconsignal is received by the system, the database probability functionwould be combined with the reader antenna probability function accordingto one or more computational algorithms to reduce artifacts likereflections, noise, and degradations, and give a more concentrated cloudof estimated locations, thus greatly increasing the probability that thetortoise is within the area defined based on received signal andprobability map.

The system operator would have the option to use either the originalsignal cloud, the probability corrected cloud or an overlay of both,over laid on a map-like or photographic representation of the area inwhich the search is being conducted. The PSF will be based on fullyupdated 3-D real-time database that 1) computes probable location and 2)displays tortoise locations. Therefore the second function of thedatabase is the more obvious one of displaying the geographic terraindata along with all recorded measurements of tortoise-relatedinformation accrued through this study, prior studies, or relatedstudies that can be used in this context. This real-time graphicaldatabase information can additionally be utilized online by anyone whoneeds access to its information. Our initial system design utilizes(besides the real-time communications network of operational systems)USGS Digital Elevation Models (DEM's) as a preliminary basis for ourgeographic database with real-time GPS inputs. The real time GPS/compassinputs will establish the exact location and orientation of each readerunit and help compute the predicted tortoise location. The actualdatabase will eventually consist of GIS-based data layers, such as soilsand land cover types acquired from various public and commercialsources. The computation of initial probability cloud by antenna signalanalysis and further refinement by the probability map are consideredessential functions of the locating system's signal processing routine.

With this refined real-time probability of location information (likelyobtained from the vehicle mounted system with the longest possiblerange), a more specific search (likely by a hand carried reader antenna)will be made, to successively approximate the location of the tag untilit is found and verified. The need for hand-carried or even smallersized mobile tracking units is based on the assumption that the primaryland vehicle might not have the capacity to explore dense shrubbery orother habitats inaccessible to the large vehicle. The exact locationwould then be entered automatically into the historical database, whichfurther modifies the pre-defined model. The hand-carried unit alsointeracts in real-time by cellular or independent telemetry with themobile unit; both are updated immediately by information detected at thehand-carried unit. Instead of guiding the hand-carried unit by antennapositioning and beep loudness, a real time map-like visual display ofthe reader, the terrain and the likely tortoise location will be used inaddition to the antenna orientation of the medium range reader.

This real-time database is an integral part of the tracking systembecause it provides increasingly accurate information about exactlocations and possible movements of tortoises for display and archivalpurposes, as well as providing the real-time probability function forcomputation of estimated location during a survey or search. For initialsurveys, the PSF system will help the on-foot researcher locate theanimals accurately with minimum effort. As the system gains historicaldata (and improves on estimation algorithms), it is possible that itwill provide a single step process (mobile tracking only) and eliminatethe need for on-foot tracking in the majority of surveys where only theanimal's location is needed.

In FIG. 1 the full scope of the location and identification system canbe realized from the combination of the various individual parts thatmake it. A tortoise 104 has an affixed tag 102, which (in someembodiments) is activated by interrogation signals sent by RF antennas108. The same antenna 108 receives long range burst signals from tag 102and the signal, likely amplified by RF preamps 116 recorded withequipment such as an oscilloscope 122 or spectrum analyzer 126. Thesemay later be replaced by receiving and analysis systems that do not havedisplays. The outputs of these preamp/signal analysis instruments aresent (digitized) to the computer system 132 in the primary locationsystem. A GPS 110 and compass 112 determine the position of the primarylocation system, assuming it is a mobile system. The computer system 132computes a probable location of the activated tag which is combined withGPS 110 and compass 112 data as well as historical data 130 in order tocalculate a refined area of probable location. This process isaccomplished by SOFTWARE resident in the computer 135. The softwareconsists, at least, of INTERFACE Programs to link the external devicesto the computer and digital information processing programs (applicationprograms 134). These application programs provide at least the followingfunctions: computation of the location of the LOCATING SYSTEM at whichthe signals from the tag are being received; computation of theDETECTION of a signal from at least one tag; computation of aprobability function indicating the DIRECTION from which the signal isapparently located and computation of the probable function DISTANCE atwhich the tag signal is located. This determines the first approximationof the LOCATION of the tag. This approximation is refined by a SPATIALPROBABILISTIC FILTER program, to be explained later. The resultinginformation of the location system and the PROBABLE LOCATION of the tagare then displayed on a MAP of the relevant area in terms of terrain,geographical position, geological and other features supplied from theDATA BASE 130. The DISPLAY 138 conveys this visual information withinthe primary location system, and also transmits a reproduction of thedisplay information to one or more remote stations (later diagram). Allthese functions are accessible through the CONTROL INTERFACE 140, likelyresident in the primary location system and accessible by theuser-operator 144. Information may also be sent to a remote BASE STATION142 for permanent and nonvolatile storage. The information from the maindisplay 138 and other relevant information are sent, through a separateCOMMUNICATION CHANNEL or RF COMMUNICATION INTERFACE 114 to one or moreREMOTE LOCATING DEVICES 106. One possible embodiment of remote devices106 can be used to verify the location of tag 102. Note that the remotedevice also has antennas and can be used with different RF technologiesfor closer range location of the tag, and could have its own GPS andCOMPASS to determine its position within the larger map of the primarylocation device, and generate a closer-range map (possibly incommunication and cooperation with the primary location device), and sothe close range system and its operator are also guided by visualdisplay maps and possibly other indicators to help determine theclose-range location of the tag. All close-range data is communicated tothe primary location system and the location map is continuously refineduntil the tag is exactly located. All data is recorded into database 130and may be uploaded to a base station 142 for further analysis. In thecase that the tag 102 is activated by an ACTIVATION SIGNAL sent from theprimary location system, that activation signal may be generated by theCOMPUTER which controls and activates a signal generator 120 that feedsRF power amplifier 118, which transmits the radio signal using the sameor different RF ANTENNAS that are used to pick up the Beacon and/or IDsignal from the tag. Note that the ID of the tag may be implicit in thebeacon signal and thus established upon detection of the tag in therange of the primary location system, or the ID of the tag may only beestablished at close or zero range by the secondary (on foot) locationsystem(s). Note also that the Remote (hand carried) device 108 may alsosend out activation signals to the tag. Either the primary locationsystem or the remote location system may also send out sufficient RFPOWER to supply operating power to the tag. All signals of this type(activation and/or interrogation signals from either remote or closerange transmit/receive antennas to/from the tag) are denoted by 146.

FIG. 2 shows a mobile lab which eliminates the need for fixed locationantennas and may serve as a local lab and signal processing station 205which can communicate data to and from a fixed base station. This may beespecially useful for medium and/or close range location systems.

The mobile lab carries all instrumentation and powering equipment, and,in addition, provides a comfortable living/walking space for extendedmissions in hostile climate areas. The mobile lab and its equipmentdepicted here are just one of any number of specific embodiments for the“primary location system” mentioned previously in FIG. 1 .

The Mobile Lab 200 is constructed from a modified camper-van which isable to navigate desert dirt roads in most seasonal conditions. As such,it provides all necessities for multiple day trips through the desert,including overnight accommodations, cooking, hygiene and internaltoilet, and air conditioning. To support the operation of the lab duringfixed location surveys, a 3000 watt gasoline powered generator 210 isprovided for running air conditioning, all electrical services, andstable AC power. AC is needed for running all the electronic test andcomputer equipment 205 used both in the Research and Development phasefor the system and final embodiments of the electronic and computerequipment. The lab-van has attached to its top a removable antennasupport structure 212, which can be disassembled, such that the vehiclecan use surface roads and freeways in traveling to its destinations inthe desert for its survey work. When assembled on top of the van, theantenna system is made as long, wide and high as the vehicle willsupport, either for slow but continuous travel on desert dirt roads fortaking measurements for faster survey completion or for stopping atdefinite locations along the survey route and taking measurements forgreater accuracy. In a preferred embodiment the antenna structure hasfour vertical masts extending to a total height of about 7 meters ormore. Height of antennas is very important in finding signal sourcesthat are either embedded or are on the surface of the desert substrate.Preferably the sources are as far as possible above foliage and rockswhich progressively attenuate radio signals in a straight line pathbetween the lab-van and the tags. This will be discussed in more detaillater. Distance between antennas is also maximized to provide the bestpossible accuracy in “triangulation” estimate of tag locations. Theseestimates are based on arrival time of tag signals at differentantennas, amplitude of signals, and other aspects of signal that can besensed at different but precisely co-located antennas. A GPS /compassantenna at a central (or other definite) location of the antenna arrayprovides the location of the lab structure and consequently the locationof each antenna on it.

Many types of antennas may be used, and it is contemplated that multipleantennas will be used on each mast. For example, antennas 201, 202 and203 and 204 may be omnidirectional “whip” antennas at ¼ wave or ½ wavelengths, depending on the frequency in use. The omnidirectionalantennas, while not as sensitive as some other types, provide a welldefined receiving point from which arrival time, waveform shape andother location-determining information may be derived from any signalsource equally, in any direction from the antenna array. Antennasnumbered 207 (for all locations on array) may be directional “YAGI” typeantennas which provide good signal gain at the resonant frequency, in aparticular direction as differentiated from other directions. Theseantennas may be mounted facing at fixed directions to obtain betterdifferentiation of direction of incoming signals. Alternatively they maybe mounted on rotatable mechanisms. In this embodiment they may be sweptcircularly like radar, to scan the area omnidirectionally but with moresignal gain than with nonpolarized antennas. The antennas may also beselectively rotated until the highest signal input is obtained from eachantenna, further helping to accurately calculate the apparent positionand distance of the signal source.

More directional antennas such as parabolic beam-forming reflectors mayalso be mounted on the mast and used in a manner similar to thedirectional YAGI antennas. Additionally the highly focused beam-formingproperties of parabolic antennas (or similarly motivated designs) may beused to direct outgoing “wake-up” or powering energy to directions oflikely tag location, delivering signals that may be strong enough toeither “wake up” or even power a tag for return-signal generation. Lessdirectional antennas would not direct enough energy.

The van-lab may also carry temporary fixed point masts and antennae (notshown in diagram) which might be powered either by a cable from the vanor self-powered by battery, solar or generator power. These antennaswould provide more distant “triangulation” points without thedeleterious effect of permanent masts (that could provide housing orvantage points for predators).

FIGS. 3A and 3B show tags that are shaped as to fit on the scute of atortoise where it will least obstruct the animal from its dailyactivities and growth. A special glue 310, such as presently used forlarger tortoises, can be used to affix tags onto tortoise scutes thatwill last and not adversely affect the animal in the long run. FIG. 3Cshows location marker tags can be used to mark historical locations oftortoises.

FIG. 3E shows a medium to close range handheld or backpack mountedreader-locator that is used in order to find and validate the locationof a tortoise given a probable location provided by the spatialprobabilistic filter. Two antennas 343 and 344 can be used totriangulate a close range RF signal from the tag, and this informationcan be uploaded to the primary location system with a communicationsantenna 342. The advantage in this is that the close-range locator maynot have the computation power to perform location within its ownprocessor, but the information could be computed by the primary locationsystem (computer) or tags and relayed back by the communication channel.This also allows the primary system to keep track of all secondarylocation units (of which a plurality may be dispersed to find the tag atcloser range). This handheld locator has a display similar to a GPSdisplay, but with specific information for its operations terrain, andcontinuously updated probabilistic location information derived from itsown signal receptor and data processing. The secondary locating devicemay have its own GPS and compass to provide its exact location back tothe main system, or this may be accomplished by the main system throughtriangulation of the more powerful communication or tag interrogationsignals emitted by the secondary locating device. The secondary locatingdevice may use different tag location and ID technologies and/orfrequencies than the primary unit, since, at close range, a tag may bemore easily powered by externally generated E-M fields. Because variousclose-range (1 to 100 meters) RF transaction activities take placebetween the tag and the secondary reader, a wide variety of technology,antenna and form factor choices for both the tag and the secondaryreader/locator occurs as a result of the “multi-stage, multi-technology”approach.

FIG. 3F shows a mobile lab that eliminates the need for fixed locationantennas and may serve as a local lab and signal processing stationwhich can upload data to a fixed base station. Likely not necessary inview of FIG. 1 .

FIG. 3G shows a relatively fixed-location base station 360 that collectsall the information from all sources (or from the primary mobilelocation system via a stronger ratio channel) and compiles them into amain database that can be used for further analysis.

FIGS. 4 5, 6 are charts showing the engineering trade-offs encounteredin all forms of technology evaluation and product design as applied tothis particular specific system for tortoises. These charts also showthe construction of an “end-to-end” physical and electromagnetic modelof the entire environment of the operation of the system to be designed.This model will then serve as an aspect of the probabilistic spatialfilter system, which depends on a model of every determinable aspect ofthe system operation (in general and in each specific “location and IDsearch” performed by the operational system. Before certain modeling andsimulation tools (interactive systems of Solidworks, COMSOL, E-Msoftware, circuit modeling software) were available, the concept wouldbe too complex to be executed by available computing power, and thusinoperative. However, this model itself (physical model, electromagneticsignal model, circuit models, and system models) in its real-timeoperable mode is now not only feasible, but serves also an intrinsicelement of the location system, acting in real-time with observationdata and signals, location maps, spatial probabilistic filter, displaygenerators, and two-way real-time communication links between allseparate location apparatus of the system. At this time, it is possibleto create an interactive data feedback system with a correctly designedmodel, detailed data on the physical environment, and detailed data onthe animal the tag is attached to and a model of the interaction of theprimary locating vehicle with the actual terrain (as well as that of thesecondary locating vehicles). This system is an improvement over priorart techniques, in that it would be able to facilitate the mosteffective system design and continuously optimizes the probabilisticlocation filter process and thus the actual operation of the system foreach location task in its useful operational life. A beginning point maybe the association of the tag with the tortoise and the tortoise withthe substrate in which it lives.

FIG. 4 is a system evaluation diagram, stratifying the various aspectsthat are important to designing the best tag to fit on a juvenile deserttortoise. The tag is to be a device that may fit on a single scute ofthe young tortoise and also accommodate its growth. The tag may containlayers 400 of conductive, semiconductive, insulating or otherelectrically active materials. The bottom of the tag is attached to theouter shell on one of the scutes. The scute-shaped tag body may be usedas antenna or part of an antenna. The attachment (glue or tape) might beconductive or nonconductive. Wires 410 may extend over the shell as longas they can be made to be harmless to the tortoises growth, whichinvolves the accretion of the material between the scutes that hardensinto different growth rings around each scute. Wires down the shell maybe useful as antennas or parts of antennas. At the central part of thetag there may be a raised area 420, as long as it would not exaggeratethe natural shape of the shell too much. A raised area would beconvenient for locating electronic components comprising part of thetag.

Note that the tortoise will almost always be in physical contact withthe substrate or ground 430 on which it lives. The electrical impedanceof this contact may possibly be used as a design factor, oralternatively it may be eliminated as a design factor if no good use forthe variable impedance connection can be found and no significant effecton operation is expected. The impedance and surface features of thesubstrate (ground, earth, sand, burrow, clump of plants) on which thetortoise lives will affect the electromagnetic design whether or not theimpedance from the tortoise to the ground is utilized in the systemdesign. The distance between the tag elements and the ground surfacewill affect the radiation and reception of the antenna, and it is sureto vary as the animal rests, moves, hibernates, and grows. In generalthe following aspects of the tortoise itself as a physical object mustbe considered in the tag and system design: Shell surface impedance,shell to bony layer impedance, internal body impedance (to varyingdegrees of detail), body-to-ground impedance, tag-to shell interfaceimpedance, etc. 440. These aspects of the tortoise-as-system-componentare listed in 440.

Items 450, 460 and 470 concern sources possible for powering the tag.Since tortoise always go out in the sun when not in hibernation to heattheir bodies to optimum levels for metabolism and movement, a solar cellon the tag surface is optimum for powering the tag as well as fordetermining when the tortoise is in the optimal position/location forits tag to be read. The presence of sunlight means the tortoise isgenerally above ground and in relatively clear overhead space. Thereforethe presence of sunlight makes and solar power converters 450 possible abattery-less active tag, and in addition can work with other circuitryin the tag to utilize as much sun-power as possible to broadcast beaconand ID signals, as well as to charge any secondary batteries orcapacitors (or super capacitors) in the tag circuit.

One or more batteries 460 may be a part of the tag circuitry. In thecase of a secondary battery, it can be used to power the tag electronicsystems and can be re-charged by a number of energy-harvestingtechniques (solar, motion-generated electricity, electromagnetic field),or even directly electrically recharged if the tortoise is able to bephysically handled. A primary battery may be used as a circuit componentto power a clock-calendar circuit. These batteries and the ultra-lowpower drain circuitry mentioned, as used in digital watches, have lifespans of several years when running ordinary watch and LCD circuitry. Ifused to power a clock-calendar circuit that schedules the times, daysand months that surveys are likely to be successful, their only functionwould be to turn ON or OFF a CMOS switch to enable tag activation. Thisshould allow the battery to operate much longer, and battery life toapproach its shelf-life and certainly long enough to power only ascheduling memory for any passive OR active tag functions that might beutilized. Since batteries can now be made very thin and flexible, eitheror both batteries might also serve a double function by occupying alarge surface area of the tag and utilizing one or both conductiveterminals as part of the tags antenna structure 470. The function of abattery serving as part or all of an antenna is known in prior art.(e.g., Beigel prior patent application and/or patents) Related to thetag design is the implementation of an indelible identification numberassociated with the tag and/or the tortoise. The most reliable method ofproviding an indelible memory element in a tag is laser or otherwisephysically/electrically fused PROM tag number 480. In addition to beingindelible electrically, it can also be examined microscopically and readoptically if only remnants of a non-working tag or deceased tortoise arefound. This also brings up the possible desirability of subcutaneouslyimplanting a PIT (Passive Implantable Transponder) under the skin of thejuvenile tortoise. Present PIT tags can be made small enough for thispurpose without causing a weight burden or danger of infection to thetortoise, and therefore should be able to serve as a “back-up” to anymore advanced long-range transponder mounted on the shell of thetortoise.

The external components (not connected and distant from the tortoise)listed in 490 indicate some of the components of the reader-locatorsystem at the “other end” of the system design, for example, Signalgenerator, component analyzer, preamps, antenna, computer system, DSPand database software. In addition the environment between the tortoise,tag and reader-locator (not numbered) must be considered in the SYSTEMAPPROACH to the design, modeling and ACTUAL OPERATION during thedeployment of the system. This basically summarizes the “end-to-end”approach in which simulation, design, physical implementation ofcomponents, and operation of the entire system during its entirelife-cycle are part of a UNITARY FUNCTIONAL METHOD of providing this tagand location system.

FIG. 5 shows a tag detection location and identification system thatworks according to a tiered hierarchy of function plus utilization. TheSYSTEM 500 consists, as discussed in FIG. 4 , of the tortoise or objector asset, the tag or identifying modality, the environment in which theID/Location system operates, the locating/identifyinghardware/software/transport, and the real-time database that computes,displays, tracks, and possible predicts the location of all thetortoises, objects or assets, covering the past, present and predictablefuture time line of the study being conducted.

The stratification of this system in 500 depicts the notion of “layers”within the process of system components, operation, and useful output.The elements in 500 are the primary stages of system functions forlocating the tortoise: Detection (finding a signal that may be from anID tag), Detection of any signal that could be a tag signal, Direction(as determined by time-of—arrival, relative signal strength, etc at theprimary location system's antennas), Distance (which may be obtained ifsufficient signal allows accurate triangulation), and Location (whichderives from the first three “D”s and the known location and orientationof the “reader” system. Identification may be independent of location(it could be implicit in the signal pattern, or it might only be foundby directly accessing the animal). The Location process 500 may alsoproceed in stages, in which a provisional location is computed by theprimary location system and the precise location is determined byadditional short-medium range location system(s) dispatched to the areaof approximate location.

System aspect 510 concerns the models of electromagnetic signaltransmission from tortoise (or asset) to primary and secondary locationsystems. It is “layered” in the sense that first the “tortoise” model isconsidered, then the tag model. Together they form the firsttransmission model. They (tortoise & tag) interact with the “closeenvironment” (ex. Borrow, pallet, open space, sand, etc.) model of theenvironment, substrate, nearby vegetation or RF obstructions, and takentogether form a sub-system that could be considered a “transmitter” intothe mid-range and long range spatial models. The close range objectsthat interact with the antenna can be lumped together since they maydetermine the signal strength, directivity and polarization of theoutgoing signal that traverses the (possibly) much longer distancethrough the environment to the long range location station (as anexample). Likewise, a corresponding transmission model from the “reader”to the tag would be constructed for system types in which the readersends a signal (either providing power or query information) to the tag.

Signed processing 520 refers to a “macroscopic” mid and long-rangemodels of transmission of the signal through foliage and air, includingmajor obstructions, air attenuation, and major reflections. This aspectapplies to both “tag to reader” and “reader to tag”. Signals reachingthe antenna structures pass through an additional model of the antennasand the preliminary signal processing. The signal (presumably nowdigitized) passes into the detection, direction, distance models, theoutput of which is mapped onto the terrain map model. At this point thespatial probabilistic filter model 530 interacts with locationprobability clouds generated by the preliminary location processingsystem, and determines the most likely location areas, which can bemultiple on account of reflections, etc. A second round of computation(not shown in FIG. 5 ) occurs when sub-location information istransmitted by the short range location systems, and the probability mapis updated until, by successive approximation of location, the tortoise,object or asset is positively located and identified. In other words,the location process is repeated. This data point becomes a historicalasset for the entire location system. The display functions at theprimary and secondary location systems then involve the human operator'sintelligence and experience in discerning the graphic map informationwith real life in order to actually locate the tortoise. In this way,the concept of layered models becomes the process by which the systemoperates and improves its function by accumulation of historicalinformation and successive correction of the various computationalmodels corresponding to the physical object of interest, the physicalenvironment, the electromagnetic environment, the hardware and softwarelocating devices, and also the improvement of human interpretation ofdata and use of the system.

FIG. 6 shows a procedure followed by the spatial probabilistic filter,which may be resident as software or firmware in the primary (longrange) location system and possibly also the secondary (short range)location systems.

Flow chart 600 shows PROCEDURE STEPS IN IMPLEMENTATION OF SPATIAL

Probabilistic Filter:

Step 605 is Send signal to request tag information (optional, tag may beself-activated) in “beacon signal” modeStep 610 is Receive signals either from transmitter or transpoder(amplitude, phase, arrival time, etc.Step 615 is Calculate first probability clouds of signal source(s)relative to the antenna system geometryStep 620 is Receive location information for antennas (i.e. the GPSbased location of the antenna bearing device (long range or short rangelocation systems)

When the signal coming in from a tag is analyzed by a particularlocation-estimating algorithm based on the relative signal values at theantenna locations, it is unlikely, especially in the case of a weaksignal in a complex environment, to be a single “location” calculated.More likely there will be a probability density function of possiblelocations clustered around one or more central locations (in the case ofreflections, it is likely that numerous “locations” will be calculatedwith no real way to decide a preference of one over another. This is thefirst “probability cloud” generated by the signal processing of antennasignal data.

Then, there is the second probability map based upon the topography ofthe general area in which the antenna data are received. The generationof a “probability map” from a topographical map requires anunderstanding of numerous aspects of both the topography, terrain, andthe possibilities and habits of locomotion of the tortoise (or otheranimal, object, asset, etc). Some obvious examples in the case of thejuvenile tortoise serve to illustrate—only superficially-what the artand science of constructing a “probability map” can entail. In thesimplest model, one can impose a binary (0,1) model: either the tortoisecan possibly be at a certain location or cannot possibly be there. Forexample, a tortoise cannot be inside the center of a large solidboulder: so probability=0 for an area or volume occupied by such anobject. In a sunny area free from obstructions, the probability might bedefined as 1 because the tortoise COULD be there. From this crudest“possible/impossible” weighting function for the 3D space inconsideration, one would develop finer gradations based on more detailedstudy or statistical experience of locations confirmed. For tortoises,the knowledge that they like to nest in certain clumps of plants, or thelocations of known tortoise burrows, or could not be in closed buildingsinto which they cannot access, can build up a “gray scale” ofprobability density regarding the various known aspects of thegeographical area under study. Changes in the area must not beneglected. Removal of foliage, change of terrain due to flooding of washareas, etc. must be monitored and the probability map updated tomaintain the best accuracy and relevance.

This probability map concept can apply to the acquisition of positiondata for any item of interest in any environment. The requisiteconditions are a map or diagram of the environment and the structureswithin it, or other dimensionally calculable aspects which would affectthe likelihood of a target object occupying any point in the space. Thelocation of the system making the measurement of distance and directionto the target object must be known. The history, if any, of sightings ofthe objects within the environment should be known if possible. The sizeof the object, its characteristics regarding movement direction andspeed, capability of sustained motion, etc should be known. The objectdoes not have to be tagged, for example, visual sightings or radarimages might be used to estimate its location instead of tagtransmission data. Thus, the probability of one or more objects being ina given space in relation to the location finding system may beestablished to varying degrees of accuracy, and the over-all accuracy ofthe estimation of the objects position may be enhanced by themathematical combination of the probability map with all other locationdata (and uncertainty) obtained by the measurement system. However, thisprocess is only the first of a possible sequence of steps taken toprovide the exact location of the object.

Step 625 is Calculate location-map information: Place the locationsystem (readers, antennas) within a map model of the local environmentGPS based on history and new information (step 630).Step 630 is Receive GPS and GIS data on location topography: adddetailized data regarding substrate, foliage, objects, topography)corresponding to possible location.Step 635 is Receive historical data on objects to be located, based onprevious confirmed locations and computation of all possibletrajectories from previous historical records that could place an object(tortoise) within the general location area based on its maximum travelrates, possible travel paths, etc.Step 640 is Mathematically combine first probability cloud with a secondprobability function generated by 3D map and historical data.Step 645 is Display resulting location probability map (refined):Assuming a human operator (since a robotic or automatic artificialintelligence operator might also be used and a display map not needed),the display would for example show a topographic map of the area inwhich the measurement search is taking place. The location of theprimary locating system and the orientation of its antennas would bedisplayed on the map display, derived from GPS and compass measurements.The probability cloud of possible object locations would also bedisplayed on the map. The spatial probability function (based on eitherhuman judgment or possibly an algorithmic derivation) would besuperimposed on the map, in regions corresponding to the probabilitycloud. Finally, the enhanced probability cloud would be displayed oraccentuated within the total display.Step 650 is Since multiple tags may be detected simultaneously by thesystem, a refined probability cloud for each tag would be separatelyprojected onto the display and differentiated from any identifiablydifferent tag probability clouds. Send fine-detail system closer intoprobable location: At this point, if a more accurate or completely exactlocation of the tortoise is desired, the second (or nth) stage oflocation equipment would be brought into the situation. For example, thebackpack mounted or handheld location system (which may use an entirelydifferent technology for location and/or ID) would be dispatched to thearea or areas of highest likelihood of location.Step 655 is Communicate location of fine-detail system AND large scalesystem, and further refine probability of location of object:

The close range system's position and orientation, likewise derived byGPS and transmitted on a “communications channel” to the primarylocation system, would then begin seeking the tagged tortoise. Since itsrange is short, it might not have data to report until it has comecloser to the tortoise. However, its trajectory would be tracked by itsown GPS system, relayed to the primary station and displayed on theterrain map. Since the close range system also has a display, andreceives a visual image of its location, orientation and trajectory fromthe primary system, the close range seeker will not be aimlesslywandering in search of the tortoise. If it has traversed all possiblearea in the probable location region and found nothing, it can then moveto another region of probable location. Since the range of the closerange system is known to a relative extent, it can even be directed asto how closely to survey the area to avoid needless repetition with outmissing an area. Assuming the tortoise is located precisely; itsposition is marked on the main map. Its ID is read and any physicalhandling necessary may be performed. If its ID tag is rechargeable byelectromagnetic field, the short range reader might be brought close toit for the required period of time for a re-charge. The system describedis a two-stage system, but there is no need to limit the systemoperation to two stages if the geographic area is very large, orincreased accuracy is needed, or the limitations of locating equipmentrequire more stages to exactly locate the object. The probability map isalso then updated and the probability functions corrected by the exactlocation information, and possibly an analysis of “wrong guesses” andtraversal by the short range system.

TAG: The above description described a tagged object, however similarmethods may be used to find un-tagged objects if methods of successivelyestimating its location are available, and the notion of a spatialprobability map applies to successively accurate estimation and finalexact location.

Tracking Software

Mathematically, the antennas will pick up a signal y from the tortoisein position x. This signal will be complicated, potentially includingcomponents from reflections and interactions with the terrain, alongwith noise, W. The problem can be posed as one of finding the position Xfrom the measurement y. That is, we want to maximize the probabilitythat we would receive the measurement y under the assumption that thesource is at position X for a given set of (antenna) parameters, θ.Mathematically, the problem is maximizing the conditional probabilitywith a set of constraints

$\begin{matrix}{{\max\limits_{x,\theta}\Pr\left\{ {y{❘{x,\theta}}} \right\}},{{s.t.{{x - x_{previous}}}} \leq {vt}},{{{x - x_{rock}}} \geq \delta_{rock}},{{{x - x_{surface}}} \leq \delta_{surface}}} & (1)\end{matrix}$

The constraints listed here may not be exhaustive, but rather serve asan illustration of the kinds of constraints envisioned at this point.The constraint ∥x−x_(previous)∥≤vt says that a given tortoise cannotmove farther than vt since the previous observation at time interval tin the past. The software should record the time of each observation ofeach tortoise and thereby eliminate erroneous detections by properchoice of the maximum velocity v. Of course detection at very longdistances might still be a valid detection if the tortoise was carriedby a predator, flood, or other unusual event—and the software might wantto record these events as well. Similarly, the last two constraints saythe position cannot be within rocks or a distance farther thanδ_(surface) from the surface.

To solve this problem, we first formulate a model that containsinformation about the terrain, and estimates the measured signals y thatwould be detected from a source at x for some set of parameters θ. Thismodel may be of the form y=ƒ(x,θ)+w. If the noise is Gaussian whitenoise, then we can write this problem as one of searching for theposition X that minimizes the estimation error e=∥y−ƒ(x,θ)∥. This is astandard optimization problem (Boyd2004) and SC Solutions (a Californiacompany, for example) has developed tools for solving these types ofproblems.

Thus for the software development there are three main tasks. The firstis a model that estimates the antenna signals that would be detected fora source at a specified location with possible variable parametersassociated with brush, moisture, and other variable factors that canaffect the transmission for the RF signal. This task will be undertakenusing commercially available software (COMSOL). The source strength anddirectional pattern will be assumed known (and calculated from the “endto end” electromagnetic system model).

The second main task is that of integrating a terrain map and thetransmission model into an optimization module that reports thedetection of a tortoise position by solving Eq.(1). For the fullimplementation, the software must detect multiple tortoises and performthe necessary transformations from the coordinates of various antennasmounted on (Mobile Laboratory, Hiker, UAV, etc.) to the coordinatesnecessary for solving the optimization problem. For example, the modeldescribed above (y=ƒ(x,θ)+w) will be duplicated for each antenna withits unique parameters θ associated with its position within the terrainso that the global position predicted, X, will be accurate. Since themodels for various antenna/detection schemes may be different for thevarious modes of detection and are likely to evolve and improve withtime, this model integration should be sufficiently modular and genericto allow easy accommodation of future detection improvements.

The third main task will be to integrate location information of thetortoises with a real-time geographical database. The database will alsoserve as a repository for historical data as well as real-time GPS andGIS data. It can be used to help the on foot searcher locate the animalsmore accurately and provide updates to the model y=ƒ(x,θ)+w in terms ofterrain features.

Algorithm projects spatial probability cloud onto GIS map powered byUSGS.

Compares the projected probability code with a pre-computed spatialprobability surface derived from the known information about thelocality

Historical; geological; temperature; solid objects; etc.

Projects a refined spatial probability display on the map surface basedon the comparison algorithm in which Tag emits an id/location signal:

-   -   Long range detection system picks up at least part of the signal    -   Assigns a direction based on time of arrival, frequency        modulation, other signal properties    -   Assigns a distance according to signal analysis, amplitude,        Doppler, frequency content, etc.    -   Assigns an ID based on code or signal burst distance    -   Computes a preliminary probability cloud of direction, distance,        ID based on calculations from above signals and signal        processing algorithm derived from the signal properties and a        general topology of the surface or 3D volume within range of        signal reception.

FIG. 7 shows a parabolic antenna. This type of antenna is very efficientfor forming a beam-like signal dispersion pattern, resulting in the mostefficient transfer of energy to a tag or reception of signal from a tagat longest distance. However, the antenna must be large compared to thewavelength of the signal or the effect cannot be successfully achieved.Accordingly, this type of antenna would be restricted to UHF ormicrowave frequencies for effective use on a mobile platform, becauseotherwise the antenna size would be too large to carry. Note also that abeam-forming antenna is appropriate only when a reasonable estimate ofthe object's position is already known, or when there is sufficient timeavailable to rotate the antenna to cover all possible directions withsufficient overlap between beam patterns for transmission and receptionof signal or for power.

FIG. 8 shows that a carrier signal is seen in the data stream as aseries of on and off periods. Of the many possible ways for signal powerand/or data to be transferred, a method called “on-off-keying” may beused. This simple method turns a carrier signal on or off according to apredetermined pattern which may represent the ID code or other fixed orvariable information.

FIG. 9 shows FSK MODULATION TRANSITION OF RF ENERGY.

In another common modulation method, the signal is transmittedcontinuously, but the frequency is different for each “value” ofinformation to be transmitted. As shown, periods of determined timevalue or numbers of cycles of frequency F1 and periods of frequency F2(both within resonance capture by an appropriately designed antenna) maycorrespond to digital “0 and 1” respectively, while allowing theadvantage of a continuous RF signal for (example) powering a remote tag.

Note also that a first carrier wave of a first frequency which is onehalf the frequency of a second carrier wave, and e.g., the sameamplitude, may be modulated by a digital wave where “zero” uses thefirst carrier and “one” users the second carrier, for a modulatedresultant wave.

FIG. 10 is a Spatial location map of a tag and reader and the associateddirect distance/direction line. (NOTE: this diagram might be placed inproximity with FIG. 6 for clarity). An example display in connectionwith a “spatial map” might appear as in FIG. 10 , which itself depicts a“landscape” at an appropriate scale and orientation relevant to thelocation search. Item 1010 may depict the center point of location ofthe primary and secondary location systems. Item 1000 may depict thecenter of a probability cloud of estimated location of the tag. Item1020 depicts a “straight line” trajectory between the locator and thetag, indicating both the approximate direction and approximate distancefrom the locator to the tag.

FIG. 11 shows a simulation of a “scute tag” on a tortoise shell and alsoillustrates some aspects of the physical modeling system. In the figure,1100 depicts the close-range substrate in the locality of the tortoiseshell. A mock-up drawing of the outline surface of a TAG 1110 isdesigned to fit on top of a particular scute of the tortoise. However,this illustration is over-simplified in that it does not (and cannot ina still—life illustration) show the powerful modeling system beneath it,which creates the images. The tortoise shell itself can be viewed fromany perspective, at any distance. Furthermore, the shell can “grow” insize while the tag components remain at their original size and positionon the portion of the scute they started on. Likewise, the SUBSTRATE canbe viewed from any position or scale of distance. The shell can befilled in with detailed simulation of the “inside” of the tortoise, as asimple impedance or detailed with internal organs. The PHYSICAL MODEL ofthe tortoise and tag can interface with the ELECTROMAGNETIC model of thetortoise, tag antenna, near, medium and far environment. The circuitryon the tag can be simulated with a circuit simulation program thatconnects to the antenna radiation simulator, and so on, such that theentire physical domain from microscopic to multi-kilometer, along withthe electromagnetic domain of the same range of scales, along with thecircuitry and signal processing simulations of the components andsignals can be “seamlessly” simulated with available technology, i.e.,COMSOL and ORCAD and SOLIDWORKS and others. As mentioned previously,these models can be linked to the results of field measurements forverifying and improving the correspondence between model andexperiential measurement. At a certain point of development, thecorrespondence may be determined to be so accurate that the need forfine-scale verification may become less important, and the periodic“inventory” process of tortoises (objects or assets) in a givenenvironment or survey space, may be greatly simplified as the process ofmodel-verification-feedback-improvement matures. Model, actual devicessurveys, and database, are interactively optimized at chosen timeintervals creating a continuous incremental improvement of all of theseaspects of the “project operation” based on: experiment history,technology advancement, continuous model, survey and databaseimprovements.

FIG. 12 shows an oscilloscope trace which shows the time of arrivaldifferences from a distant electromagnetic pulse source, received by tworesonant antennas as an array located at nearby but different points inspace. As an example of an input-stage signal processing method forsignals received for tags, the fast (300 picoseconds per division)horizontal scale of a 1 GHz oscilloscope shows the pattern of a singlesignal generated by a “pulse” source received by each of two identicalYAGI antennas about one foot apart and parallel to each other, bothpointed in the general direction of the pulse source. Antenna 1 signal(upper signal) and antenna 2 signal (lower signal) appear on channel 1and channel 2 as decaying sinusoidal waveforms created by the resonantantenna response to the pulse signal. The small difference in time ofreception of the signals indicates an angular displacement of the pulsesource from a center line between the two antennas. Based on this angle(and possibly also the average amplitude and relative amplitudes betweenthe signals from each antenna), a calculation of estimated DIRECTION ANDDISTANCE of the DETECTED signal provide the basis for calculating the“probability cloud” estimation of the pulse source's position. More thantwo antennas may be used for better estimation of directionality anddistance.

FIG. 13 shows the diameter and details of a prior art miniatureelectronic tag which provides a complex function for visual detection ofpet animals in the dark. Such a tag is within the skill of those ofordinary skill in the art. The facing surface of the tag isapproximately 1.0 centimeters in diameter. Not shown on the tag are apattern of printed circuit traces, electronic components includingresistors, capacitors, a control IC (integrated circuit) and an array ofLED's are all arranged on a substrate coated with a photo resistivematerial. The assembly is covered by a clear epoxy dome. Although it ispowered by batteries larger than would be employed on the “tortoise tag”of the present invention, this commercially, reasonably priced itemshows that a complex tag with various sensing, control and signalingfunctions can be produced on a platform the size of a juvenile tortoisescute.

FIG. 14A shows various small telemetry tags. Item 1400 shows a piece ofconductive foil, cut to a typical “scute” size and shape appropriate fora juvenile desert tortoise scute. Placed on the foil is an actual sizePHOTO of a telemetry tag that has been developed and successfullydeployed on large dragonflies, and tracked as they migrate through theair. While the device developed for the dragonflies would NOT work forthe tortoises for many reasons, the picture adequately demonstrates thata device of similar complexity but different specific components andfunction could be deployed on a “scute” tag. Item 1410 is the same photoof the “dragonfly tag”, but not mounted on the scute shaped conductor.Item 1420 is an actual working “PIT” (passive implantable/injectabletransponder) tag that is 8 mm in length, and which provides close range(under 50 centimeters) identification at a 134.2 KHz low-frequencyinductive-coupled technology platform, and could be mounted on ascute-tag substrate, or on another surface location on the shell of atortoise, or even implanted under the skin of a juvenile tortoise as aform of permanent positive ID tag and/or portable database.

FIG. 14B shows a small tag. Such a telemetry tag may be used to trackdragonflies in flight. Dragonfly tags, made by Sparrow Systems Inc, havebeen used to track migrating dragonflies for time lengths up to about aweek. They use a relatively low (165 MHz) telemetry frequency and have arange of over a kilometer when the dragonfly is in the air. They need athin wire antenna about 2 inches long, perpendicular to the fly's bodyto attain this.

FIG. 15 shows a mockup of a tag on a tortoise in a desert environment.The tag 1500 fits over a scute of a juvenile tortoise 1510 (for thisphoto a tortoise shell is used as well as the sand, gravel and smallrocks are commonly found in a “close range” desert environment.) andsetup for this demonstration photo.

FIGS. 16A, 16B show a combination of several RF modules to create amultifunctional tag with RFID and Harmonic Radar capabilities. Thefollowing diagrams depict inventive designs that would fulfill therequirements for tags that could be mounted on small (and growing)juvenile desert tortoises, and would meet the necessary conditions ofsize, weight, performance and durability required for the tracking andcensusing project that led to this invention development. Therequirements include:

A Detection range of 1 KMLocation to an exact point during surveyUnique ID for a population under 1000Acceptable to use multiple ID technologies/location methods or multipletags on one animalA Tag weight of less than 2.5 gramsA Tag operation of at least 1 year with no servicingThe tag must stay on the animal as it grows

The next diagrams describe various approaches, methods and components toproviding the required tag for the tortoise example. Providing a generalpurpose tag for small animal, large animal, object and asset locationmay use any of the features described in the present invention, as wellas other features appropriate to the size and shape of the animal orasset to be tagged and tracked.

FIG. 16A shows HARMONIC RADAR AND RFID WITH SAME ANTENNA:

A combination of several RF modules to create a multifunctional tag withRFID and Harmonic Radar capabilities. Prior art had demonstrated 16 mmlong wire/diode tags that could be mounted on flying insets, but couldnot provide individual ID, and further required kilowatts of power in aradar beam at 9.3 GHz directed primarily above the ground surface (andto some extent also above foliage cover). For implementation of the sameconcept on ground-living tortoises, the long range detection goal couldnot be achieved because of ground absorption of the signal and possibleinterference with the harmonic generated by the tag on account of semiconductive mineral objects on the ground substrate which could alsogenerate harmonics. However, it is anticipated that medium range (10meters to 30, and possibly up to 100 meters) detection and locationrange can be achieved with longer wavelength signals at lower powers(i.e. 900 MHz-2.4 GHz fundamental frequencies). To add individual IDcapability to a harmonic radar tag the present invention provides:ANTENNA 1600 is a dipole or patch or bowtie (or other form) of antennathat can receive the incoming signal at fundamental frequency, and whichcan contain a microwave (and/or schottky) diode in the geometric middleor other viable geometric section of the antenna so that the antenna canre-radiate the second harmonic of the incoming frequency when it (theincoming power at the incoming frequency) contains sufficient energy todrive the diode into its nonlinear conductivity region.

NON-LINEAR DEVICE 1610: the nonlinear device may be a microwave orschottky diode, or in general any electrical component that has a strongnonlinear response at a relatively low power input. A pair of diodes mayalso provide a nonlinear, but symmetric transfer function. 1620 RFIDCIRCUIT connected across, for example, a single schottky diode may be anRFID circuit (either passive, semi-passive, semi-active, or active) thatis activated either at the same input power level as the nonlineardivide in the case of battery or other “assisted power” RFID circuit, orat a higher power level in the case of a passive RFID circuit, and whichmodulates an individuating code or other signal either as a secondarymodulation of the harmonic generated by the nonlinear device, or as anadditional signal to the nonlinear device-generated signal.

FIG. 16B depicts an RFID device in parallel with a harmonic radar tag.The harmonic radar tag functions as usual, providing second harmonicenergy across the two quarter-wave sections of a half-wave tunedantenna. When the RFID device functions (either passively, as the energylevel of the signal allows a sufficient DC potential to develop in acircuit across the diode and power the RFID circuitry or semi-passivelyor semi-actively in which the signal across the diode provides a“wake-up signal to a battery or solar powered RFID device), it may forexample close a switch according to a predetermined ID code sequence.The switch may provide a relative short circuit across the diode forbrief time periods, allowing the reflective second-order harmonic signalto be modulated by the RFID code (while still allowing enough power toremain in general across the diode circuit to keep the RFID deviceactivated or powered.

DIPOLE ANTENNA 1630: Preferably tuned to resonate at the chosentransmission frequency band (for example 902 to 928 MHz for UHF or 2.45GHz for microwave tags) RFID CIRCUIT 1640: May be any type of circuitdesign that either derives power from a signal impressed across thediode, or that is appropriate for the generation of harmonics whendriven above its nonlinear threshold SCHOTTKY DIODE 1640A: Passivelypowered and is activated (or “awakened”) by the electrical signal acrossthe diode received by the DIPOLE ANTENNA 1630

FIGS. 16C, 16D show a carrier signal that is seen in the data stream asa series of on and off periods if the diode is open circuited, or a fullsine wave if the diode is short-circuited by a shorting switch acrossthe diode terminals within the RFID circuit, as known in prior art RFIDcircuits.

FIGS. 17A, 17B show an embodiment of a series version tag. SERIESVERSION TAG 1700 is simply another version of an RFID plus harmonicradar tag. DIODE 1705 is in series with RFID circuit 1710. It is assumedthat the RFID circuit presents a “switch closed” circuit at least untilit is activated by the increasing DC voltage developed across itsterminals by the increasing signal to the diode through ANTENNA 1715 andANTENNA 1720 to develop a DC voltage across the terminals of 1710. Theseantennas may be two quarter-wave sections of a half-wave dipole antenna,or alternatively any other configuration that is capable of absorbingand emitting RF energy at the transmission frequency and its secondharmonic (twice the transmission frequency) or a higher harmonic, or aharmonic series.

SERIES SWITCH MODEL TAG 1725 depicts a typical embodiment of an RFIDcircuit that might be used with either the serial connected tag 1700 orwith the parallel tag shown in FIG. 16B.

DIODE 1730 is connected between the two parts of a half wave antenna(ANTENNA 1750, ANTENNA 1755). The SWITCH 1745 in series (oralternatively in parallel as in FIG. 16 ) with the diode is actually the“Modulating element” of the RFID circuit, and can take numerousalternative forms. The RFID element depicted here essentially consistsof three parts: power supply 1735, RFID circuitry 1740 and modulationswitch 1745. The power supply is developed from DC voltage stored fromthe rectified AC voltage, in this case rectified by the microwave diodeLikely the RFID tag may have an additional diode or diode bridge orequivalent, and capacitor in the power supply so that at low levelsignal inputs it does not load the microwave diode (because its owndiodes have a higher threshold voltage) and in that way does notdiminish the range of communication for the harmonic radar localizingcircuit. The RFID circuitry consists of at least a clock signalextractor or generator, a counter, a memory circuit and an output to themodulating circuit (being controlled by the code in the memory asaccessed by the counter). The modulating circuit is simply a switch(with some intrinsic switch resistance). Other more complex modulationcircuits employ a switch and some other components. For example, FIG.17C shows a switch “control” and a capacitor C1 in parallel with anothercapacitor C2, functioning to change the effective series capacitanceaccording to the RFID signal. FIG. 17D Contains a switch “control” 1770in parallel with an inductor circuit L, providing a shorting of theinductor in accordance with the RFID circuit. FIG. 17E likewise providesan incremental resistance change by switching “control” to shortresistor R1 in series with the diode. Thus, FIG. 17E simply shorts aresistor by the incremental resistance of the switch. FIG. 17F switches“control” a capacitive reactance C1 in parallel with a resistor R1. FIG.17G switches “control” a resister R1 in parallel with another resistorR2. These and other circuits combing solid state switches with otherelectronic components may be used to optimize a particular RFID tagcircuit for the most appropriate modulation of a reflective tagimpedance at a given frequency and for particular types of RFID readersignal acquisition and analysis circuits.

FIG. 18 and its counterparts make use of a circular “ring” type antenna,generally used at microwave wavelengths. In FIG. 18A a simple conductivering 1800, will resonate at an RF wavelength corresponding to itscircumference and can produce a damped exponential waveform in responseto a strong pulse waveform from a reader antenna. The diameter could bevaried by definite steps to provide a small amount of frequencydifferentiation for identification of a small population of objects oranimals. In FIG. 18A, conductive ring 1800 might be adhered to ordeposited on a passive substrate 1830, or alternatively a piezo ceramicsubstrate 1820, or piezo film flexible 1810 to provide additionalreaction to an input pulse. This is achieved by the resonance of thering providing mechanical deformation of the piezo substrate or thecurrent/voltage around the ring providing piezo electric deformation onthe substrate and thus generating additional voltage as a result of theinteraction. In FIG. 18C, a diode 1820 inserted within a break in theconductive ring 1815 may produce a second harmonic ringing output inresponse to a pulse input at the ring's fundamental resonant frequency.FIG. 18D uses two diodes, 1830 and 1840, in opposite directions tomaintain AC conductivity of the main ring antenna while still producingharmonics due to the diode nonlinear characteristics. FIG. 18E utilizesa diode-harmonic reflector “ring” antenna 1815 and passive or activeRFID circuit 1850 in the same manner as the circuits of FIG. 17 , but inthe context of a ring antenna.

FIG. 19 depicts a semi-passive, semi-active or active RFID tag inconnection with a harmonic radar tag. Antennas 1970 and 1980 provideresonant response at a fundamental frequency and the second harmonic ofthe fundamental frequency. Microwave diode 1940 provides harmonic outputat the second harmonic when activated. The remaining components providevarious methods of delivering power to an RFID circuit 1850, which mayoperate in a “reflective” manner as described in FIG. 17 either“passive” if the RFID tag derives all its energy from the externallyinduced signal, or “semi-passive” if the tag has its own separate energysupply, but still operates by load switching across the diode. 1960.Additionally, the RFID section may operate in various “active modes”that may add energy to the resonant circuit according to the RFIDinformation, and/or also through terminals (s) 1960.

For powering the RFID tag, the energy from the diode circuit may be usedas in the purely passive RFID case, but in addition the RFID circuit maybe powered for example by a solar cell charging a capacitor or abattery. A strong field at resonant frequency may also charge thecapacitor or battery through diode for extended useful operating life1930. When sufficient input signal is detected, a wake-up signal 1960activates the RFID tag (without drawing any power from or limiting theeffectiveness of the harmonic radar tag). The existence of the signalallows the self-powered RFID tag to produce an RFID function. It maymodulate the second harmonic generated by the diode, or in addition mayadd a powered signal to the terminals across the diode, transmitting anRFID signal with much greater range than would a passive RFID tag, andpossibly greater range than would the harmonic radar tag.

In such a case, the signal generated by the microwave diode would allowfor a much wider range of RFID detection once the tag is activated by amicrowave signal. The power for the semi-active or semi-passivecircuitry may come from a SOLAR CELL 1910 charging a capacitor orsecondary battery 1920. In addition, a strong RF signal received at theantenna 1970 may flow through charging diode 1930 to re-charge thebattery. This is only likely in a situation in which strong RF energy isbeamed to the antenna AFTER detection of the tag by harmonic radaroutput, or after the tag has been located and accessed to charge thebattery from a short distance with a strong local RF field.

Saw Tags and Saw Tag Combinations

Harmonic radar devices have been explained in some detail above, howeveranother class of devices exist that need to be mentioned. These are SAWID tags. SAW or Surface Acoustic Wave tags are based on the propertiesof piezo electric crystals (and likely other piezoelectric materials. Ifa piezoelectric crystal is stimulated with an electrical pulse signal,the dimensional deformity produced by this travels down the surface ofthe crystal as an acoustic wave. Upon meeting an electrode spaced alongthe crystal, an electrical impulse is generated with a time delaycorresponding to the speed of sound on the material and the distancetraveled. A pattern of electrodes at different lengths along the crystalwould yield a pattern of electrical pulses at time delays correspondingto the arrangement of the electrodes. This phenomenon may be used in anidentification./location device by adding a resonant antenna to contactwith the exciting terminal and the responding terminals along the piezocrystal. This provides an interesting kind of ID/location tag sincethere is really not an electronic circuit (in conventional terms) to bepowered by a minimum power level transferred to the device. Essentiallythis means that the range of activation and response of a piezoelectrictag is only dependent on the signal-to noise ratio of the antenna andamplifier of the receiving antenna and/or the magnitude of pulsed fluidallowed by regulations or attainable by power input into thetransmitting antenna. The transmitting and receiving antennas may be thesame antenna, and the lack of interference between an outgoing pulse andthe incoming pulse (delayed by distance traveled to and from the tag)incoming pulse allows for single antenna operation as well as veryaccurate radar-like distance estimation. Combinations of Harmonic radarand SAW tags in combination, in much the same way as harmonic radar andRFID tags in combination. And even combinations of all threetechnologies (Harmonic, SAW, RFID) on a single tag are contemplated.

FIGS. 20A-20C show an embodiment of a harmonic RFID radar tag which usestransformer coupling to achieve the RFID effect.

Shown in FIG. 20A is a HARMONIC RADAR RFID AT UHF OR ABOVE whichconsists of: HARMONIC RADAR TAG 2000, made with microwave diode 2005 andpossibly an additional tuning impedance at the midpoint (NOT NUMBERED),and a half-wave 2006 antenna at microwave or UHF fundamental frequencyfunctioning as described earlier in this disclosure. Additionally, FIRSTINDUCTOR 2010 has two terminals connected across the diode terminalswhere the antenna joins the two terminals of the diode. Inductor 2010may have the combined function of providing resonant tuning of theantenna (in connection with the intrinsic capacitance of the microwavediode, but which also has a second function as the primary of atransformer operating at the fundamental frequency or alternatively atthe second harmonic frequency. The SECOND INDUCTOR 2015 provides thesecondary inductor of a transformer made up of 2010, 2015 and theirmutual inductance and turns ratio. This provides an electricallydecoupled, but reactively coupled, source of energy or signal for RFIDtag 2020. RFID tag 2020 may be either active having its own power (solarcell, battery, etc.) or passive (i.e. it may or may not have a source ofelectrical power separate from the energy transmitted to it through thetransformer formed by 2010 and 2015). The harmonic radar tag is designedto transmit a harmonic signal when activated by a UHF or microwaveincoming signal, and provide a detection signal (without identification)at maximum distance dictated by the optimized design of the harmonic tag2020. The RFID tag, if passive, may function at a closer range whensupplied with excess energy from the microwave diode, either at thefundamental frequency or the second harmonic or both, as design options.This extra energy may be in the form of a DC polarization across thediode terminals or excess AC voltage across the diode, or both. Apassive RFID tag would in the schematic shown, be powered by AC signalreceived at the transformer secondary 2015 through terminals 2021 and2022. Additionally the RFID tag, if active, may begin transmitting anRFID signal and/or modulating the second harmonic from the microwavediode as soon as sufficient signal is detected through the transformerto “wake up” the active tag. In the case of a “step-up” transformerwhere the turns ratio of coil 2015 to 2010 is significantly greater thanone, it is possible that the RFID tag (especially if it's active) mayfunction as soon as the microwave diode produces enough signal to “wakeup” the active tag. Other design options are also possible as may beobvious to one skilled in the art.

FIG. 20B shows an example embodiment of an RFID tag 2050. Terminals 2021and 2022 are connected to the terminals of the secondary coil of the UHFor microwave transformer 2020. Alternatively, in a non-inductivelycoupled version, the terminals 2021 and 2022 may be connected directlyacross the microwave diode terminals 2005 directly or for someembodiments, or through one or more capacitors (not shown). Within theRFID tag 2050 (which may be an example of RFID 2020 of FIG. 20A), forexample, a bridge rectifier made of diodes 2025, 2026, 2027, 2028 (orother rectifier circuits used in prior art RFID tag circuits whichinvolve FETS connected as rectifiers in place of two or more of thediodes) provide a rectified full-wave DC output derived from the signalinput.

It should be noted that the design of the rectifier circuit can beutilized differently for an active or a passive tag. For example, in apassive tag the sum of the voltage drops for activation of the full waverectifier circuit will be significantly higher than the voltagenecessary to create second harmonic radiation by the microwave diode2005. This voltage margin will allow the RFID tag circuitry to benegligible as a load on the microwave harmonic radar tag until thesignal strength has risen to a point where the diode bridge turn-onvoltage is activated. For this reason the harmonic radar tag retains itsgreater range of operation and detectability and the RFID function turnson at a higher signal input (closer range). A similar function may beprovided by a single diode RFID rectifier, in which the harmonic radartag diode is a schottky diode and the RFID tag diode is a silicon diode,with a significantly higher turn-on voltage than the schottky diode. Theidentification function of the RFID tag begins to operate when thetracking antenna has come closer to the harmonic tag. The signal leveltransmitted to the tag by the external reader/locater may be increasedupon detection of the locating second harmonic signal from the microwavediode, in order to activate the RFID function at a further distance thenif the transmitted signal were held constant.

In the passive RFID tag, charge is accumulated across capacitor 2035, orin an active tag the excess energy from the diode bridge may be used tocharge 2035 if a rechargeable battery is used instead of a capacitor(BATTERY 2035). In either case the terminals of 2035 are connected tosupply power to the RFID circuit. One of the lines connecting terminal2021 or 2022 to the RFID circuitry may supply the RF signal as a clocksignal, or the RFID circuitry may develop its own clock signal as knownin prior art. Likewise, the voltages output of the diode bridge or otherrectifier circuit may provide a threshold signal to wake up or turn onthe modulation function of the ACTIVE RFID circuit, rather then justsupplying power (to a passive RFID circuit.

RFID Circuitry 2040:

RFID 2050 is an EXEMPLARY CONFIGURATION OF RFID 2020. Through terminals2042 and 2041 the RFID circuit may either switch a load in and outacross terminals 2021 and 2022, or, in an active tag, an RFID circuitmay also provide an active RF modulated signal to terminals 2021 and2022, and thus through to the antenna 2006 to achieve greater operatingrange for reception of the RFID signal.

FIG. 20C depicts a graph of one possible mode of operation of a combinedharmonic radar/RFID tag. The vertical axis depicts the ACTIVATINGelectromagnetic field input from a reader to the tag antenna or in theregion of the tag, while horizontal axis depicts, qualitatively, thetype of signal output from the tag. At very low signal input levels,region 2058, the tag is basically inactive. It might backscatter anincoming radar signal at its fundamental frequency as an ordinary radarreflector. As the field intensity increases, the microwave diode isactivated to its nonlinear conductive region and the second harmonicsignal is transmitted along with the reflected fundamental frequencysignal giving the harmonic radar tag function range (2060). As the inputfield strength becomes stronger, the RFID section of the tag begins tooperate either passively (or actively. This may dramatically change therelationship between the start of harmonic radar tag function and RFIDfunction.) Then the RFID tag signal output region 2070 is achieved, andthe tag may provide both identification and location information bymodulated backscatter of the second harmonic or an actively transmittedRFID signal at the same or different frequency.

FIGS. 21A-21C shows an example embodiment of a scheduled transmittertag. Many options for design embodiments exist for this architecture,and it is noted that the embodiments of FIG. 21 represent only threeexamples.

In FIG. 21A, the general architecture for a scheduled tag is depicted.Scheduled transmitting tag 2100 is a tag that contains an internal clockcircuit, or perhaps another type of sensing or timing circuit, thatdefines a calendar and/or clock function for the possibility ofoperation of the tag. The term possibility is stressed since the“schedule” may only define calendar or clock schedules when the tagMIGHT be operational. In one embodiment, the tag would function wheneverthe schedule allows operation, in another embodiment, the tag mightfunction when the schedule allows operation and an activating signal issensed by the tag. In yet another embodiment the tag might function whenthe schedule allows operation and there is sufficient sunlight or otherambient power available to activate self-powered operation without powerdrain on the clock/calendar battery. In this case, the tag mighttransmit a BEACON signal periodically (independent of receiving anyactivating signal from a reader) as long as the sunlight allowsself-powered functioning. In another embodiment the tag may work as inthe first three descriptions but may also be forced into operation by an“emergency wake-up” signal even if operation is not scheduled and evenif internal clock/calendar battery is used.

The main idea of the schedule is to save tag energy for time periodswhen it is known that a survey of tags may be conducted, or to preventoperation when it is known that animals such as tortoises would be inplaces inaccessible to light for powering solar cells and in badlocations for location and ID transmission, etc., i.e., that asuccessful communication would not be possible.

The primary elements of a scheduled-operation tag are primarily aclock/calendar self-powered by an ultra miniature (and/or flexiblethin), long lived battery. The power consumption of the clock/calendarmust be minimized to the extent possible by numerous techniques known inthe art. The battery must likewise have as high a charge capacity aspossible for the size allowable in the tag design. Simple LCD watcheshave been known to last many years on a single battery, and thisincludes (at least) driving a small LCD display. The calendar circuitrymentioned here would not even have to expend display power, it wouldsimply count time and turn a CMOS switch “on or “off” at specified timesof the day, week, month and/or year. The programming or reprogramming ofthe calendar schedule memory could be done electrically orelectromagnetically from close proximity at deployment, or upon are-capture—release cycle during census periods in a scientific study.The clock 2110 uses a low-frequency crystal 2134 for timing accuracy,though other clock-signal elements might also be used, and the clocksupplies time/date to schedule program memory 21151. Assuming theschedule has been set appropriately, when scheduled operation isindicated, the conditional operations of the tag are then activated byenvironmental sensors to further validate the option of expending energyfrom any of the tag energy use systems. Light sensor 2105, which couldbe either a solar power cell or a conductive light sensor, might enablea “transient logic” section 2120 if the sensing of light indicates thetortoise is above the ground, on a sunny day, and not under a deep coverof bushes. Is the transient logic is enabled by both the light sensorand the schedule program, then the tag is “armed” to transmit a “beaconsignal.” In this example the tag is also equipped with an RF receivingantenna 2145 which might also function as a transmitting antenna.

A secondary power source in the tag may be either a re-chargeablebattery 2137 and/or a capacitor or supercapacitor 2136. This powersource may be charged possibly by a Solar Array 2141, 2142, 2143 througha rectifier diode 2144, or by DC energy RF field through RF antenna 2145and RF-to-DC converter 2130. When sufficient power is accumulated withinpower storage elements 2137 and 2136, the tag is then switched into a“signal transmit” mode. Power supplied to the TRANSIENT GENERATOR 2125is enabled by the TRANSIENT LOGIC to be switched as a high-current pulseinto the TRANSIENT ANTENNNA 2146. The transient antenna is a high-Qresonant antenna which emits a “ringing waveform” exponentially decayingelectromagnetic field into space at the antenna's resonant frequency.This might be in response to an interrogating signal received by theANTENNA 2145 from a reader searching for tags; or it may be generatedindependently as soon as sufficient energy is available. Additionally, asuccession of pairs of transient pulses with definite programmedtime-delays between each pulse of the pair (generated by the transientlogic) may enable an identification of the tag by the time-delay betweenthe pair of pulses, differently coded for each tag in the population.The time length between each pair of pulses would be long in comparisonto the time length of each pulse of the pair, thus creating a series ofself-identifying “ringing” transient wave forms for the tag when it isscheduled, activated by favorable external conditions, and interrogatedby a reader within operating range of the tag.

FIG. 21B

-   2150 RESONANT ANTENNA-   2151 RESONANT ANTENNA-   2155 INDUCTOR-   2160 CAPACITOR-   2165 RCSE-   2170 SPARK GAP-   2175 DIAC

FIG. 21C

-   2180 PV CELLS

FIG. 22 shows a synchronized resonant antenna with transmitters ondifferent scutes. Two or more tags are mounted on the tortoise shell2200. Of these tags, the 2210 ACTIVATION TAG may be a scheduled tag asmentioned earlier, or simply a tag that can sense and respond to aninterrogation of “wake-up” signal from a reader or interrogation device.This activation tag may be passive, semi-active or active, and may bepowered by signal from the reader, or external energy such as sunlightor an internal battery or a combination. The Activation tag outputs asignal which may be a beacon signal, a “flashbulb” type signal, and mayor may not have ID information encoded in it.

The activated tag 2220 responds only to the signal generated by theActivation tag, in determining the frequency and timing of its outputsignal. It may, like the activation tag, be passive, powered by sunlightetc, or battery powered. The purpose for having an activator tag and anactivated tag is to increase the signal level and the directionalcoverage of the ID signal emitted by the tags on the tortoise. Each tagis mounted on a different scute 2230 on the tortoise, and assuming thatthe wavelength of the RF frequency emitted by the tag set issignificantly larger than the distance between the two tags, the signalwill have more omnidirectional coverage and power than would the signalfrom a single tag. The activated tag derives its clock frequency andtransmission timing merely by picking up the signal transmitted by theactivation tag and “repeating” it by any appropriate circuit/systemmeans.

FIG. 23A-23D show example embodiments of a scute tag, i.e. an RF tagthat is appropriately sized and shaped to fit on a scute of a juveniledesert tortoise. Other tags of similar design that different in size,shape, height or other aspects may be assumed to be obvious to use onother animals, objects or assets.

FIG. 23A depicts a scute tag which has numerous components and radiatingelements mounted on it and attached to it. RFID CHIP 2300 is mounted on2310, a conductive radiating element of a patch antenna. Cover 2305 forchip 2300 protects the chip from the outside environment, and may beopaque or clear. If it is clear, it may function as a solar concentratorfocusing light on a solar cell integral to or mounted upon the chip. Thechip is assumed to be a functional RFID chip of an appropriate type asdescribed already or subsequently. The antenna radiator element is madeup of an appropriate combination of a conductive patch 2310 and asmaller “radiating” patch separated by a dielectric material fromanother conductive patch 2311 of a greater surface area. Conductivepatch 2311 is generally defined as the “ground” terminal of a patchantenna. In addition, and taking advantage of the biologicalconstruction of the shell of a desert tortoise, a wire antenna 2315 maybe attached to the top patch antenna 2310 and possibly another wireantenna 2316 may be attached to the larger “ground” element of the patchantenna 2311. This hybrid antenna can be designed so that the radiatedsignal would be greater than either the patch antenna or the two wires,dipole antenna(s) alone, by presently available modeling and designtechniques. The wire antennas can be draped along the tortoise shell asshown in later diagrams.

Antenna 2317 is also possible as an additional radiating surface,directly inherent to the RFID chip or mounted upon it. This would make acomplex antenna with three radiating surfaces as opposed to the twousual radiating surfaces of a conventional patch antenna, as well asadditional wire radiators attached to terminals on the patch antennasurfaces.

FIG. 23B is essentially a side-view of the device of FIG. 23A with someadditional detail. Dielectric insulation 2320 is shown betweenconductive surfaces 2310 and 2311 of the patch antenna. The thicknessand the dielectric constant of the insulation, as well as theconductivities and facing surface areas of the two conductive surfacesbounded by the dielectric insulation are factors that determine thefrequency of resonance and the “Q” or radiation gain of the patchantenna.

The tag device is attached to the shell 2325 of tortoise by an adhesive2330. Various types of epoxy, cyanoacrilate and other types of adhesiveshave proved successful for long-term mounting to tortoise shells. Theadhesive also has electromagnetic properties. Adhesive 2330 may beinsulating with a particular dielectric constant, or conductive to agreater or lesser extent. In any case, the coupling by the adhesive ofthe tag, the tortoise shell scute, the body of the tortoise within theshell, and the electromagnetic “connection” between the body of thetortoise and the “ground” upon which the tortoise rests or moves; areall relevant to some extent in determining the electromagnetic couplingbetween the “patch” antenna (or more complex patch plus wire antenna)and the ground and surrounding near space. Consideration of the likelyrelation between the tortoise and this near electromagnetic environmentwhen a transmission or data transfer takes place can be used to optimizethe antenna and tags electronic design so that it performs best when thetortoise is in the most likely position to facilitate the besttransmission of the signal transfer, as opposed to other possiblepositions of the tortoise with respect to its “near” environment.

In FIG. 23C, RFID TAG 2335 is coupled by COUPLING DEVICE 2340 to be inparallel connection or coupling with HARMONIC DIODE 2345. Harmonic Diode2345 is coupled on both sides to generally resonant antennas 2350 and2351. The antenna structure in general is resonant at a fundamentalfrequency and also at twice or an integer multiple of the fundamentalresonant frequency. When a signal received at the antennas the resonantfrequency is sufficient to power the harmonic diode into nonlinearoperation, allowing the re-radiation of outgoing signal at twice or “n”integral number of times the resonant frequency from the incomingsignal. The tag then functions as harmonic radar reflector.

If the signal re-radiated from the tag is of sufficient strength toprovide extra power signal to either activate or operate a passive oractive RFID tag, then the tag may either send out its own separate RFIDsignal through either or both antennas, or modulate the harmonic signalfrom the harmonic diode with an RFID code across the diode to transmit abinary 0 bit or not shorting the diode to transmit a binary 1 bit, toconvey the tag ID message. If the RFID tag is active or semi-active,then it is also connected independently to power supply 2355 for RFIDtag. In this case the RF tag only requires the presence of an activatingsignal from the circuit comprised of the antennas and the diode, and mayoperate at, above or even below the threshold of activation of theharmonic radar tag as long as its power supply provides power forindependent operation. In that case the ID tag may be assumed as simply“sharing” the antenna structure with the harmonic radar tag. To someextent the tag of FIG. 23C is similar to FIGS. 16-17 and 19-20 .

FIG. 23D depicts a number of identification and/or location device tagssharing the same physical package, and/or the same antenna(s). In apreferred embodiment, three tag functions share common elements ofpackage, antenna, and electronics.

Patch antenna 2360 as described previously, may provide either or bothan absorbing or radiating antenna (either or both) of a harmonic radartags, possibly including half or quarter wave wire antennas 2315 and2316. Antennas 2315 and 2316 may be attached to the patch antenna or maybe independent of the patch antenna. The UHF RFID tag might be passiveor active, and might use antennas independent of the harmonic radar tagor in common with it. In addition a LF/RFID tag 2365, a separate IC chipattached to an inductive antenna wound on a ferrite core and operatingat a frequency of 125-150 KHz, may be packaged within the samescute-sized tag but be entirely independent electromagnetically andphysically, in terms of ID code, of the other combined or independentUHF tag and harmonic radar tag). All, essentially, comprising a singlepackaged unit but up to three independent functional circuits. Thissynergy and redundancy can serve any number of useful purposes for long,medium and short range location/identification to increased reliabilityand operational lifetime. In addition, for example, the LF passive tagmight be independent of the other tags, hermetically sealed andimplanted within the body cavity of the tortoise to assure lifelongclose range identification independent of the operation and attachmentof the other tag to the scute of the juvenile tortoise.

FIGS. 24A-24B show top and side views of an embodiment of anencapsulated oval shaped tag, appropriate for use with this system. Theoval shape is for example only.

In FIG. 24A the oval-shaped tag has an oval shaped ground conductor2410, an array of chip-type solar cells 2400 for solar power generation,chip protector 2405, and a radiating surface. A hemi-sphericalprotective cover is placed or formed over the maincontrol/communications chip 2415, located nominally in the center of thetag structure and positioned on top of alternative energy storage andother layers of the vertical structure of the tag. This chip optionallyhas RFID active and/or passive function. It may have an antenna surfaceintegral to the chip. It may also have photoelectric and or infraredsensing/power generating surface. The Chip protector/radiating surfacemay be transparent, translucent or opaque, or may admit infrared lightbut not visible light. The surface may be an insulating dielectric ormay have an insulating inner section and a conductive surface layer forradiating signal energy. For any tag design, the safety of the tortoiseis preserved by having the heat absorbing properties of the tag surfaceroughly equivalent to the area of the scute that it covers.

FIG. 24B is a horizontal view, showing the stacking of variouscomponents, substrates, etc. Controller/pulse generator chip 2415 can bemultifunctional in any number of ways described in this disclosure orknown to present art of RFID chips and/or radio transceiver chips. Chip2415 may receive electrical power from the solar cells 2400, which mayor may not charge a BATTERY 2420, a primary or rechargeable batterymounted underneath the controller chip. Miniaturized thin batteries areknown to present art.

Multi-resonant patch antenna 2425 may be a combination of a number ofconductive, insulating dielectric, energy storing dielectric, andantenna structures on the control chip. Thus the combination ofconductive surface 2410 may serve as the ground plane. An energy-storingdielectic layer 2430 separates conductive surface 2405 from the groundplane. The energy storing dielectric may be a super capacitor orsecondary battery with internal resistance that can support an RF signalacross it, and may receive DC energy from the solar cells 2400 orrectification of RF signals received by the resonant antenna via a dioderectifier (not shown), and still be used as a dielectric to space apartthe two conductive layers to form a patch antenna. The patch antenna maytherefore be resonant at a frequency defined by conductive layers 2410and 2405, and in addition be resonant at a different frequency withrelation to the antenna formed on chip. The different resonantfrequencies may be utilized for power derivation from one resonantsection and signal generation from the other section. The signal fromthe chip section may be a short but energetic impulse, which will causethe lower resonant structure to ring at its resonant frequency andharmonics.

Adhesive layer 2435 attaches the tag to the tortoise shell, and may beconductive or insulating. If conductive, it will electrically couple thetag to the outer shell. The outer shell 2440 is relatively insulating,however in a live tortoise the underlying bone 2445 and internal bodyorgans 2450 are conductive. The legs or bottom shell of the tortoisewill likely contact the desert substrate. By including all theelectromagnetic properties of the tag, the shell, the internal organsand the contact to substrate ground, and by using sophisticated presentart modeling techniques, the entire tortoise is modeled as a componentof the electromagnetic system. Optimization of the RFtransmitting/receiving system thus formed will be more effective thanmerely modeling the tag design independent of what is attached to it (atortoise or another animal or an object, possibly in relation to orcontact with a substrate or ground).

FIG. 25A-25B show an embodiment of a combined active VHF millimeterwave/light wave tag. In these tags it is assumed that a highly directedbeam of energy is incident upon the tag. As opposed to tag architecturesin which the PRESENCE of an RF field of sufficient intensity to activateor power the tag is assumed, for these directed energy type tags theassumption is that a focused beam of energy is “aimed” such that theenergy is directly incident on the tag. This might occur in situationswhere tag location is already approximately known and energy can bescanned in the general direction so as to cover all possible locationswithin a relatively narrow angle of search, or that a broad search wouldinvolve a considerable amount of time or a very efficient method ofsweeping a directed beam over a wide angle of scan. Also of importanceis the attenuation of obstruction or foliage with respect to therelatively short wavelengths likely to be used (with a reasonable sizeddirected beam antenna) in the “beam” approach. Over the range of shortwavelengths likely to be used (likely 2.4 GHZ to over 300 GHz, theattenuation properties of obstructions foliage and even air can varygreatly, and the possibility for narrow frequency ranges which have muchhigher penetration rates of foliage, obstructions, or atmosphere can bechosen to give greatly enhanced results for reception of a beam-likesignal by a tag. The choice of reader (or activator) locations whichminimize the amount of attenuation due to foliage or obstructions isimportant. Generally a HIGHER location of the beam-forming emittingantenna (from the reader or activator) will result in less distance tobe traveled through attenuating materials on or near the ground, so ahigh mast or an airborne reader/activator might be best for a situationin which desert tortoises are the asset of interest, in a desertenvironment with low-growing foliage, for example.

FIG. 25A depicts a tag that has VHF or UHF RFID passive or activefunction, and in addition has light or millimeter wave functionincluding reception, reflection, directed reflection and emission. Theactivation of the tag might be either the VHF/UHF system or themillimeter/lightwave system, and the response might be either, or theactivation by one and the response by the other, depending on theapplication.

COMBINED ACTIVE VHF AND MILLIMETER/LIGHTWAVE TAG 2500 is potentiallyactivated by INCOMING RADAR BEAM 2505 or INCOMING SUNLIGHT OR MM WAVES2510. In addition it may be activated by RF WIRE ANTENNA 2515. The RFtag may be active or passive, consisting of 2535 IC, BATTERY.

For the beamed incoming signal (millimeter or lightwave,LIGHT-CONCENTRATOR, AMPLIFIER, EMITTER 2520 is a dome shaped apparatusenclosing a LIGHT SENSOR, PHOTOCELL 2525 or the like on the surface ofthe tag, and its distinguishing features will be explained in the nextfigure. In response to a stimulating (interrogating) signal from eitherthe UHF/VHF or the lightwave inputs, the RFID IC 2535 may respond withan outgoing signal (either having ID information or only locationinformation) either through the VHF-UHF antenna or by OUTGOINGSTIMULATED EMISSION 2530 such as by an LED or laser diode located on orintrinsic to the ID chip, and radiated out through the optical assembly2520 covering the chip.

The tag of FIG. 25B may be a tag similar to the one in FIG. 25A, withthe addition of a special construction of the OPTICAL COVER 2520.

FIG. 25B shows the detail of elements 2540 and 2550 indicating that itis a semi-circular or a dome made up of a collection of micro-spheres ofsome material that is optically active or responsive. An integratedcircuit 2545 or a photo cell or an integrated circuit with a photo cellis shown. The photo cell might be a photo sensing, photo emitting, orphoto voltaic power generating cell as any one of the number ofcomponents of integrated circuit 2545 which could also be an integratedcircuit having a whole computer and communication system on it as wellas a radio transmitter as well as possibly an opto-transmitter and areceiver.

At the high end of the microwave and the low end of the optical range wefind an area where waves behave optically and we find an area where fora small device which is a quarter of an inch in diameter approximately.A dome a quarter of inch in diameter and out of spheres that areanywhere from a millimeter in diameter more or less, the dome assemblyis a continuous “bug eye” of spheres. These spheres can act as a retroreflective element for incoming beamed wave forms. A beam of light or itmight be a beam of terahertz or a very high gigahertz waves would havethe property that if the wave came in at a certain angle and it hits thespheres that it would be reflected back at the same angle by at leastsome of the spheres. In that way either identification or at leastlocation or determination of the existence of a device that reflected anincoming wave of a very high frequency could be confirmed by thereceiver location. That by itself is something that has utility since itcan a similar function as to that which harmonic radar performs at alower frequency to provide detection from a beamed source just due tothe reflective action of a hemisphere that is made out severalmicro-spheres of an optical character. They might be made of glass ortransparent plastic. In addition, because of the development of activematerials, the spheres might also be made of a material which has anon-liner response to an incoming wave such that it could receive anincoming wave at a given frequency and emit or reflect a wave at achanged frequency in the same direction that the incoming wave camefrom.

It is also be possible that element the material that the spheres aremade to store energy and upon activation by a light or RF frequency itmight release the stored energy reflecting back a wave at a greaterintensity than the intensity of the wave it received. This kind of waveintensity amplifying material is disclosed in many of the journals ofNANO Technology relating to active optical elements. Therefore, thesematerials and retroreflective surfaces that are suitable for use withthe invention are within the ordinary skill in the art, given thepresent disclosure and the state of the art.

The state of the art also includes literature on energy storing deviceswhich when stimulated with a certain frequency release energy at agreater intensity either at the same frequency or a different frequency.Most of FIG. 25B is about that concept applied to the surface of thesphere. In addition to reflecting we assume that there is also partialrefracted energy coming in and providing a signal or wake-upinformation. If a beam is beaming in energy and it happens to hit thetag as well as reflecting back it will also refract energy and focus iton the optical sensing or emitting part of element 2545 so in that wayit can activate the integrated circuit (IC), i.e., the IC involved withproducing an identification signal or an activated outgoing signal fromthe circuit itself. In such a case, the power source need not be in thespheres and can be remote therefrom.

For example, an incoming beam of laser light might hit element 2550 andbe refracted onto the surface of element 2545. It might activate a wakeup signal if element 2545 has a source of energy available to it, eitherbattery powered, solar powered or otherwise powered, and element 2545reacted to the activating signal. Then the tag would transmit or,reflect, either the optical signal that was received and send out anoptical signal which has an ID code in response to the incoming signalthat impinged on the hemispherical coating 2550, 2540. Therefore, atleast one of sensing, emitting or photo voltaic elements would bepreferably contained in element 2545.

The sensing elements can be used to “wake-up” the circuit. Emittingelements then can be used to send out a signal through that dome thatwould get the signal to go or one of parts of the signals to go in theright direction. The photo voltaic function would mean if this objectwere simply sitting in the sun then, in essence, the lenses formed bythe hemispherical top would focus light on to it and itself could orwould be a power generating item which power could be stored in thebattery 2535 of FIG. 25A. In this way, the hemispherical “bug eye”element serves an additional purpose of providing harvested ambientlight to power an active beacon or response to a signal source.

The devices in 26B,C,D,E are essentially patch antennas which have aground plane 2640 and a dielectric insulator 2640, and the ground planeis 2650. On the top of the dielectric insulator may be placed a varietyof structures that could be optimized for transmitting variousfrequencies or wave forms including pulse wave forms is also known asultra-wideband wave forms. The first implementation 2630 is like a pointand that could be optimized for transmitting a high energy pulse waveform which could couple to the atmosphere by ionizing the air at thepoint. In that way a pulse of significant energy, that could also beresonated by the total structure of the antenna at a certain frequency,could be transmitted by this very small structure.

FIG. 26C shows a pyramidal element. Either a conical or pyramidalelement might disperse the waves or pulses at a certain polarizationwhich might be a circular polarization or another unusual polarization.Other dispersal patterns could prove beneficial in both reception andtransmission of any kind of a wave form at high frequencies. These aremostly intended at the UHF microwave or millimeter wave types ofantennas.

FIG. 26D has a hemispherical emitter, antenna emitter and also theantenna polarization with possible combinations of the above threeelements which might also be in a combination. For example 2630 might bea good conductor, 2660 might be a medium conductor and 2670 might be adielectric insulator or any combinations of those which could beenergized to optimize the antenna design for emission of a wave formusing a small antenna and emission area that would have advantages oversimple planar types of areas that are found in most patch antennas.

FIGS. 27A,B,C,D,E,F depict a collection of antenna types and methods. Itis in this case specifically directed to a tortoise which has a shellwith scutes on it. Different antennas might be placed on the animal.These shapes can be used in general applications also for tracking ofother wildlife or things.

FIG. 27A is a basic patch antenna which has a hexagonal shape; howeverit may represent any kind of a patch antenna structure.

FIG. 27B is a patch antenna, represented by antenna 2710, attachedeither at the ground plane or at the emitting section to a wire antennawhich might be tuned at a quarter wave or a half wave, resonant with theradiated frequency and compensated for the impedance of the patchantenna surface to which it is connected. It is a combination patch plusstraight wire dipole antenna.

FIG. 27C is similar except it uses two straight wire antennas, either ofwhich could be connected to the ground, either of which can be connectedto the emitter part or one of each part of the wire antenna can beconnected to one of each part of the patch antenna depending on whatgives the best results for radio transmission and reception in theparticular application.

FIG. 27D depicts a synchronized set of different patch antennas to belocated on two or more scutes of a tortoise or two or more areas on anyobject in which the size and shaper of the object is suitable for thelocation of one or more antennas within a distance up to approximately10 centimeters of each other. At least one of the antennas is “master”which generates or initiates an outgoing pulse or burst, and the othersare “slave” antennas which (since that are very close to the masterantenna) when they are activated by its emission, immediately began toalso to emit at possibly the same frequency. In this way that amount ofradiated power and the angular coverage of the radio signal emitted (orreceived) can be substantially increased by simply having multiple tags.The simplicity of the slave tags make the system less expensive and morereliable than having master tag for each one.

FIG. 27E is a spiral antenna which can be located either on the shellitself or the scute, or can be located on top of either an insulatingconductive or conductive with a insulated spacer kind of an attachmentdevice that would fit on a scute. Note that this growth of tortoise isallowed with wires over multiple scutes by providing tubes (glued toeach scute) in such a way that the wire can be pulled through the tubessimply the growth of the tortoise.

FIG. 27F is a ring antenna. 2752 represents a ring which is tunable to aparticular, likely a microwave frequency. The ring may be solid or maybe “opened” and a harmonic generating diode might be inserted as acoupling element between the two ends of the ring so that an incomingsignal might be a fundamental and the outgoing signal might be aharmonic of the fundamental enabling harmonic radar recognition. Thatwould be tuned so that the circular antenna would have a fundamentalresonance and would be able to also resonate at harmonic multiples ofthe resonate frequency.

FIG. 29 is a patch antenna in which the emitting electrode is pyramidalin shape for dispersion characteristics that are different and may havea greater angular coverage and possibly greater power dispersion than aflat area as the emitting surface. 2910 is the pyramid and 2920 is theunderlying dielectric plus conductive ground surface.

FIG. 30 shows a tortoise or an object in which a plurality of differenttechnology types of ID tags are attached to the same object. For example3010 might be a low frequency 134.2 kilohertz tag, 3020 might be a UHFtag and 3030 might be a harmonic radar tag. They may be attached asseparate tags on different points of the object and in an alternativeembodiment of that they might be all packaged together. In otherembodiments two or more tag types might share an antenna.

FIG. 33B is one example of a type of solar powered tag. When the animalcomes out in the sun, the animal does not have a battery poweredtransmitter, or if it does have a battery power, it is not using thebattery to use its energy for transmission what it is using is thesunlight energy that is gathered and it is using as much as possible ofthe sunlight energy that is gathered to provide a continuous series oftransmissions. So what happens, first of all we can look at that wehappen to be using a patch antenna of 3350 and 3351 we can equally welluse any other kind of antenna. In this case we also have somethinglabeled a transmitter and we can use many different kind of transmittersincluding no transmitter, the reason for that will become clear. On thetag outer surface are placed one or more solar cells gathering sunlightenergy, turning it into electrical energy, and charging a capacitor3335. The capacitor accumulates charge and the voltage across itincreases.

When the voltage rises above a certain level it triggers, for example, adiac or some other type of a device that immediately goes from a veryhigh resistance to a very low resistance when the voltage across it isabove its threshold. Thus it immediately transfers all of the chargeenergy from the capacitor into the transmitter circuit. In this case ifthe transmitter circuit were to emit a microwave frequency, it mightemit that for as long as the energy from the capacitor permitted, whichcould be a very short time or long time, depending on the design of thetransmit circuit. In one embodiment the transmitter might send out andmodulated ID signal.

In a different embodiment the transmitter circuit consists of only apath of electrical discharge to an electrode of the antenna, and thesignal transmitted is simply a pulse activating the resonance of theantenna, so the solar energy might cause the tag to emit a series offairly strong pulses which will become ringing wave forms of the antennaresonant frequency for as long as the animal or object is exposed to thesun. Among the ways this particular system can be used ranges frompulses which are similar to ultra wide band type transmission, toencoded sequences of pulses which ultra wide band plus an ID code if youmake a sequence of two pulses with a time spacing between them that isfixed by an ID number a full transmission of a carrier wave modulated bya coded, signal modulation wave.

FIG. 33C shows a tag, e.g., a tag like the tag described in FIG. 33B,and attaches an antenna similar to one of the earlier descriptions ofattaching a wire antenna to the patching antenna. But in this case, thewire antenna is further a harmonic tag which has a diode in it and istuned to be resonant by a combination of tuning the wire antenna withthe patch antenna. The harmonic tag might be activated much further awaythan the other kind of tag which might not be activated if it is not inthe sun or it might not be activated if it is not close enough to beactivated by a wake up signal from a reader or it might not be activatedbecause it ran out of batteries. The harmonic tag might operate as afail-safe circuit so that the item could be located and found it allother electronic systems failed. By utilizing the attachment to a partof the patch antenna, the harmonic antenna may have a greater effectiveantenna size, and a better operational distance from a reader.

FIG. 30 is an embodiment of a radar reflector tag system which includes:TORTOISE 3000

-   RADAR REFLECTOR FOR OPEN-RANGE 3010-   RFID OR IDENTITY DIFFERENTIATOR 3020-   GPR MARKER FOR INTO BURROWS OR PALLETS 3030

FIG. 31 is an embodiment of a radar reflector tag system. FIG. 31 shows:FIRST PATCH ANTENNA 3100 at a particular one of a plurality of resonantfrequencies for re-transmission of swept or stepped interrogationsignal, and a SECOND PATCH ANTENNA 3110, at a different one of pluralityof frequencies, for a two-frequency (out of a number up to about 100frequencies) identification scheme based on swept or steppedinterrogation frequencies.

FIG. 32 is an embodiment of a radar reflector tag system. FIG. 32 shows:

-   3200 TORTOISE    FIRST TAG 3210 may be resonant at a first frequency and a SECOND TAG    3220 may be resonant at a second frequency, thus identifying the    tortoise by the combination of frequencies chosen from a    multiplicity of single frequency tag resonances.

FIGS. 33A, 33B show an embodiment of a sun tag. FIG. 33A shows:

-   DIODE 3300-   SCR-DIAC 3305-   CAPACITOR 3310

Although the invention has been described using specific terms, devices,and/or methods, such description is for illustrative purposes of thepreferred embodiment(s) only. Changes may be made to the preferredembodiment(s) by those of ordinary skill in the art without departingfrom the scope of the present invention, which is set forth in thefollowing claims. In addition, it should be understood that aspects ofthe preferred embodiment(s) generally may be interchanged in whole or inpart.

What is claimed is:
 1. A system for locating or identifying a movableobject in an environment, the system comprising: a tag with at least onefrom a group of: a passive device, a semi-active device, and an activedevice associated with the movable object; a first locating device forreading the tag and emitting a signal containing at least one from agroup of: a location of the first locating device, information of adetection direction, and a distance to the tag; and a second locatingdevice for receiving the signal emitted from the first locating device,the second locating device analyzing at least one from the group of: thelocation of the first locating device, the information of the detectiondirection and the distance to the tag, and providing a location of themovable object, at least one of the first and second locating devicesfurther comprising a probabilistic spatial filter for determining aprobable location of the movable object; and a power source coupled tothe tag, wherein during a sleep mode, the tag is configured to drawpower from the power source, and during an awake mode, the tag isconfigured to be activated by a signal from the first locating device orthe second locating device, and wherein the tag further comprises anenergy storage device comprising at least one of a battery, a capacitor,a super capacitor, and an ultra-capacitor.
 2. The system of claim 1,wherein the first locating device is a mobile locating station.
 3. Thesystem of claim 1, wherein the tag is active and includes a battery andsends a burst signal on receipt of a stimulating signal.
 4. The systemof claim 1, wherein the tag is active and includes a battery and send aburst signal at a pre-programmed time interval.
 5. The system accordingto claim 1, wherein the locating device further comprise a probabilisticspatial filter for determining a probable location of the object.
 6. Thesystem of claim 1, wherein providing the location of the movable objectfurther comprises: computing an initial probability for the location bysignal analysis; refining the initial probability using a probabilitymap; and determining the location of the identification tag placed onthe object based on a refinement of the initial probability.